Nissan Electrical Components Diagnosis and Repair (1)
Short Description
Download Nissan Electrical Components Diagnosis and Repair (1)...
Description
ELTN9911B
REVISED MA Y, 2003 MAY
This book is designed for instructional use only for Nissan North America, Inc. and authorized dealer personnel. For additional information contact: Nissan North America, Inc. Corporate Training Office Technical Training 18501 S. Figueroa St. Gardena, CA 90248-4500
© 2003 Nissan North America, Inc. All rights reserved. No part of this publication may be reproduced in any form without the prior written permission of the publisher. Printed in U.S.A. First Printing: February, 1996 Revised: May, 2003
This manual uses post consumer recycled fibers
Corporate T raining Office Training Technical Training Nissan North America, Inc. reserves the right to alter specifications or methods at any time.
ii
ELECTRICAL COMPONENT DIAGNOSIS AND REP AIR REPAIR TABLE OF CONTENTS
Section 1: T ext Text Electrical Component Diagnosis and Repair Overview .......................................................................... 1 Introduction ............................................................................................................................................... 1 General Precautions ................................................................................................................................ 2 Circuit Requirements ...................................................................................................................................... 3 Source, Load and Ground ...................................................................................................................... 3 Circuit Protection Devices .................................................................................................................... 13 Circuit Controls ............................................................................................................................................. 17 Switch-Controlled Circuits .................................................................................................................. 17 Electrical Test Equipment ............................................................................................................................ 22 Analog Meters ......................................................................................................................................... 22 Digital Meters .......................................................................................................................................... 22 Ohmmeter Use ........................................................................................................................................ 23 Voltmeter Use .......................................................................................................................................... 25 Available Voltage .................................................................................................................................... 25 Voltage Drop ........................................................................................................................................... 26 Ammeter Use ........................................................................................................................................... 29 Relay Controlled Circuits ...................................................................................................................... 31 Meter and Gauge System ........................................................................................................................... 42 Spedometer Operation ......................................................................................................................... 43 Motors ............................................................................................................................................................. 44 Starting System ............................................................................................................................................ 45 Charging System Description .................................................................................................................... 49
iii
Electrical Diagrams ....................................................................................................................................... 51 Connector Symbols in Electrical Diagrams ...................................................................................... 55 Trouble Diagnosis Charts ..................................................................................................................... 61 Location of Electrical Units ................................................................................................................... 65 Foldout Circuit Diagrams ...................................................................................................................... 66 Using the Service Manual to Research Related Information ......................................................... 70 Electronically Controlled Circuits .............................................................................................................. 86 ECU Inputs .............................................................................................................................................. 87 Electronic Control Units (ECUs) ......................................................................................................... 88 Electrical Diagnosis ...................................................................................................................................... 93 Preliminary Diagnosis Tips .................................................................................................................... 94 On-Car Troubleshooting Tips .............................................................................................................. 94 Motors ....................................................................................................................................................104 Meter and Gauge Diagnosis ..............................................................................................................105 Meter and Gauge Check .....................................................................................................................107 Glossary of Terms .......................................................................................................................................109
iv
Section 2: Exercises Module 1
Locate Service Manual Information
Module 2
Intepret Service Manual Information
Module 3
Measuring Available Voltage
Module 4
Measuring Voltage Drop
Module 5
Measuring Resistance
Module 6
Measuring Current
Module 7
Combination Switch Operation
Module 8
Diagnosing One Transfer (1T) Relay Malfunctions
Module 9
Diagnosing One Make (1M) Relay Malfunctions
Module 10
Diagnosing Two Make (2M) Relay Malfunctions
Module 11
Diagnosing One Make-One Break (1M-1B) Relay Malfunctions
Module 12
Circuit Diagnosis Exercise #1
Module 13
Circuit Diagnosis Exercise #2
Module 14
Circuit Diagnosis Exercise #3
Module 15
Circuit Diagnosis Exercise #4
Module 16
Circuit Diagnosis Exercise #5
Module 17
Circuit Diagnosis Exercise #6
Module 18
How to Use a Digital Multimeter
Module 19
Fuel Gauge Tank Unit Testing
Module 20
Service Manual Electrical Symbols
Module 21
Testing Batteries, Starter and Charging Systems
v
ELECTRICAL COMPONENT DIAGNOSIS AND REP AIR REPAIR OBJECTIVES Upon completion of this training program, you will be able to: •
Given an Electronic Service Manual (ESM), locate wiring diagram descriptions and interpret the information as stated.
•
Given an ESM, interpret wiring information/diagram symbols and answer related questions.
•
Given a multimeter, a circuit simulator and a windshield wiper motor circuit, measure available voltage at different points in a circuit and make comparisons for the purpose of diagnosing faults.
•
Given a voltmeter and a test circuit, measure voltage drop as specified and evaluate the results against established specifications.
•
Given a digital multimeter, a circuit simulator, a service manual, a fuel-injected vehicle and other components, measure resistance and compare to specifications.
•
Given a digital multimeter, a circuit test kit with overlay #1, measure current flow through a circuit and evaluate the results.
•
Given a combination switch and a combination switch circuit, read a combination switch chart and diagnose various combination switch circuits using a digital multimeter.
•
Given a service manual (or ESM), a digital multimeter, a one transfer (1T) relay, circuit test kit with overlay #2, diagnose the operation of a 1T relay.
•
Given overlay #3, a service manual and test equipment, test the operation of a vehicle with 1M relay circuit.
•
Given a service manual, a digital multimeter, a two make (2M) relay and a circuit test kit with overlay #4, diagnose the operation of a 2M relay.
•
Given a test kit with overlay #5, a service manual, digital multimeter and a one make-one break (1M-1B) relay, diagnose the operation of a 1M-1B relay.
•
Given a customer's repair order, a service manual and digital multimeter, verify, isolate, repair and recheck the incident in question.
•
Given a digital multimeter, electrical components and a car, identify the different meter features, connect the test leads, and perform voltage, resistance, amperage and continuity tests.
vi
•
Given a digital multimeter, service manual and an on-vehicle tank gauge unit, test the operation of the fuel tank gauge unit and evaluate the test results.
•
Given an ASIST/ESM workstation, identify and interpret the symbols used in electrical wiring diagrams.
•
Given a vehicle, digital multimeter and model 620 tester, test the battery, starter and charging system.
vii
NO TES NOTES
viii
T E X T
ELECTRICAL COMPONENT DIAGNOSIS AND REPAIR OVERVIEW Vehicles use electricity to control and operate many systems such as headlights, windshield wipers and rear window defoggers. Today’s vehicles also use sophisticated control units and circuits to add to driving comfort and the driver's control of the vehicle. Despite the number of electrical circuits in a vehicle, troubleshooting and repair techniques used on all circuits are relatively basic and straightforward, given some basic skills. To repair an electrical problem correctly the first time, you must know how to troubleshoot and repair circuits. This course will provide you with the skills necessary to: •
Verify symptoms by attempting to operate circuits. Verify what is working and what is not working.
•
Isolate the source of the malfunction by: - tracing current flow paths using wiring diagrams. - locating harness connectors using harness layout diagrams. - testing electrical circuits using a multimeter.
•
Repair electrical problems by: - fixing broken wires and poor connections. - replacing broken components. - adjusting a switch or sensor.
•
Recheck to make sure the symptom is fixed. Duplicate conditions that caused the problem, to be sure there are no new problems.
Introduction The Electrical Component Diagnosis and Repair Course is a four day course covering diagnosis and repair of electrical systems. The Course begins with a review of electrical fundamentals followed by a series of shop exercises. The following skills are emphasized: •
Reading wiring diagrams
•
Circuit testing techniques
Each of the exercises will challenge your troubleshooting skills. The objectives for this course were carefully chosen to help you learn a more efficient way to diagnose electrical malfunctions.
INTRODUCTION
1
General Precautions •
Do not use electrical test equipment on any circuit related to the Supplemental Restraint System (SRS) unless instructed to do so by the service manual or your instructor. SRS circuits are identified by yellow insulation covering the wiring harnesses or yellow harness connectors.
•
Do not operate the engine without adequate exhaust ventilation.
•
Keep the work area well ventilated and free of any flammable materials. Take special care when handling any flammable or poisonous materials, such as gasoline, refrigerant gas, etc. When working in an enclosed area, be sure to properly ventilate the area before working with hazardous materials.
•
Do not smoke while working on the vehicle.
•
Before elevating the vehicle, apply wheel chocks or other tire blocks to the wheels to prevent the vehicle from moving. With the vehicle parked on level ground, support it with safety stands at the points designated for proper lifting or use a hoist to support and raise it if needed.
•
Before starting repairs or circuit diagnosis which do not require battery power: - Switch the ignition OFF. - Disconnect the negative battery cable
•
To prevent serious burns: - Avoid contact with hot metal parts. - Do not remove the radiator cap when the engine is hot.
•
Before working on the vehicle: - Use fender covers, seat covers and floor mats. - Be careful that keys, belt buckles or buttons do not scratch painted surfaces.
•
2
Do not touch the terminals of electrical components that are controlled electronically. Static electricity may damage internal electronic components.
INTRODUCTION
CIRCUIT REQUIREMENTS Source, Load and Ground The basis for discussing electricity in vehicles is the circuit. A circuit is a complete path for electricity to flow. Electrical circuits consist of wires, wire connectors, switches, circuit protection devices, relays and electrical loads and grounds. The conventional current flow theory traces current from the source to ground. Despite the complexity of the circuit or the number of parts in the circuit, there are three essential elements all circuits must have to operate: •
Source (voltage)—The battery and the electrical path from the battery to the load. This is the positive (+) side of the circuit.
•
Load—Any electrical component that uses electrical energy to perform work. Examples are lights, motors and defroster grids.
•
Ground—The electrical path from the load back to the battery. This is the negative (–) side of the circuit.
If any of these essential elements is missing or not working, there is no current flow and the circuit will not operate. Let's look at each of these elements. Source side of circuit Battery
Wire
Ground side of circuit Load
Wire
Source (Voltage) The source of voltage is the battery or alternator. The voltage source provides the energy to push current through the circuit, which makes it operate. The source side of the circuit includes all parts between the battery and the load. Refer to the battery rating charts (Page 46) at the end of the text section for recommended battery applications. Load A load is the device that produces heat, light, sound or motion when the circuit is operating. Light bulbs, motors and heating elements, such as cigarette lighters and rear window defoggers, are typical electrical loads. A load always has resistance and consumes (uses up) voltage when the circuit is ON. Ground A ground completes the circuit from the load back to the negative battery post. Notice that a ground path is always on the other side of the load. As important as the ground is, it is the part of the circuit that is most often overlooked. CIRCUIT REQUIREMENTS
3
Perhaps a reason for this is that technicians often think that circuit grounds consist of separate wires. Using a separate ground wire to connect each vehicle circuit to the battery is not practical. Most electrical circuits complete the ground path directly to the vehicle chassis or body. Load
¨
Negative –
Battery
Ground
When source, load and ground are all operating correctly, a complete path for current flow exists. This is a complete (or closed) circuit. An open circuit occurs when the electrical path is interrupted. This might occur when a switch is open, a light bulb burns out, a wire breaks or a wire connector becomes disconnected. Voltage, Amperage and Resistance Working circuits contain these three electrical elements: • Voltage - The electrical pressure that pushes current through the circuit. • Amperage - Flow of current moving in a circuit. • Resistance - Opposition to the flow of current. Voltage (Symbol: V) Voltage is the electrical pressure that pushes current through a circuit. Nissan and Infiniti vehicles all use 12 volt batteries, but the system operates at up to 14.7 volts while the engine is running. The charging system provides the additional voltage to keep the battery charged. Electrical current
Voltage = Electrical pressure
4
CIRCUIT REQUIREMENTS
Amperage (Symbol: A) Amperage is the measurement of current flow in a circuit. Current does not flow unless voltage is present to push it through a circuit. Research in chemistry and physics has established the electron theory to help explain what electricity is and how it is used. The electron theory states that all matter is made up of atoms. Atoms contain three types of smaller particles called: • Protons • Neutrons • Electrons Protons, which have a positive electrical charge, combine with neutrons (which have no electrical charge), to form the center or nucleus of the atom. Electrons have a negative electrical charge and orbit around the nucleus, much like the planets in our solar system orbit around the sun. Certain materials such as copper and steel contain free electrons which can be pushed from one atom to the next. This movement of electrons occurs in one direction, creating a chain reaction. The chain reaction in which free electrons move from one atom to the next is called current flow or electricity.
CIRCUIT REQUIREMENTS
5
Resistance (Symbol:
)
Resistance opposes current flow in a circuit and is measured in Ohms. Resistors are electrical devices that restrict current flow in a circuit. Because they restrict current flow, voltage decreases as current is pushed through a resistor. Two types of resistors are used in automotive circuits. A fixed resistor has a set resistance in a circuit. A variable resistor, such as a dimmer control, changes the amount of current flow by mechanically changing its resistance. Switch
Light bulb
Battery Variable resistor
Earlier, we spoke of a circuit's requirements for source voltage, load and ground. The load is the device that provides heat, light, or motion. When the resistance of the circuit load is in the normal range, with power applied and a ground connected, the circuit operates as designed. However, if either the source, load or ground is out of balance, the circuit will malfunction. For example, suppose the battery voltage drops below the normal range. Circuits such as the starting circuit cannot operate as designed. In such cases, the customer may complain of hard starting. •
Malfunctions occur when resistance in a circuit increases or decreases abnormally.
•
Increased circuit resistance can be caused by loose connections, corroded wire connectors or dirty switch contacts. These conditions create unwanted resistance that reduces the normal flow of current needed to operate the load. This causes bulbs to be dim and motors to turn slowly because voltage is used up by the unwanted resistance—the circuit has to work harder.
•
Decreased circuit resistance increases current flow in a circuit. This can be caused by a partially shorted load. The result is a blown fuse. In some cases, higher than normal current flow can overheat and burn wires and connectors.
6
CIRCUIT REQUIREMENTS
The following chart summarizes the terms we’ve just described. We'll discuss circuit diagnosis in a later section of this manual. Term
Definition
Unit of Measure
Symbol
Voltage (E)
Electrical pressure
Volt
V
Amperage (I)
Current flow
Amp
A
Resistance (R) Opposition to current flow
Ohm
Conductors Conductors are devices such as wires, that provide a path for current to flow. Some materials conduct electricity much better than others. Copper and steel are good conductors. Gold and silver are even better conductors because they have even more orbiting electrons. Since gold and silver are quite expensive, they are used sparingly on circuits such as the Supplemental Restraint System (SRS). Insulators Materials which do not conduct electricity are called insulators. Materials such as wood, glass, rubber and plastic are some examples of insulators. These materials are made of atoms whose electrons are very tightly bound to the nucleus and cannot easily move to other atoms. In vehicle wiring harnesses, the insulation isolates each wire so current flows only through the intended path. Conductors Best
m er r nu l i p d e o l o p ilv um ee a d G C S Al St Le
Insulators ir A
CIRCUIT REQUIREMENTS
r ic ic be a s t m b a l P er Ru C
Best
7
Ohm’s Law In 1826, a German physicist named Georg Ohm developed a theory about electricity. Simply stated, there is a relationship between voltage, resistance and amperage. To apply this in a practical sense, consider the following two examples: 1.
If voltage (volts) stays constant and circuit resistance (Ohms) increases, current flow (amps) decreases. Resistance (Ohms)
Current flow (Amps)
Cause
Effect
Corrosion
Dim bulb
Loose ground
Fan runs slow
12 Volts (constant)
2.
If voltage stays constant and circuit resistance decreases, current flow increases. Current flow (Amps)
Resistance (Ohms)
Cause
Effect
Short circuit
Fuse blows, circuit stops working
12 Volts (constant)
8
CIRCUIT REQUIREMENTS
Circuit Types As previously stated, all circuits must have source, load and ground to operate properly. The way in which these circuit elements are put together can be classified as either parallel, series, or series-parallel. Series Circuits In a series circuit, the source, load and ground are arranged so current has only one path through the circuit. Thus, the current flow (amps) will be the same no matter where it is measured in the circuit. However, voltage in a series circuit decreases as current passes through each load. Load #1
Source
Load #2
Switch
Current flows... Battery in one path Ground
Ground
Note Note: If the resistance of the loads are equal, the available voltage divides equally between the loads. A series circuit will operate if there are no opens in the circuit. In the circuit above, if the switch fails (creating an open circuit), no current will flow and neither bulb will light. Troubleshooting Tip #1: An open at any point in a series circuit will prevent the entire circuit from operating.
CIRCUIT REQUIREMENTS
9
Parallel Circuits In a parallel circuit there are two or more paths for current to flow to ground. The tail light circuit is an example of a parallel circuit. If one of the bulbs in a parallel circuit burns out, current will continue to flow through the other path in the circuit and the other bulb(s) will still operate. In the example below, if one of the bulbs does not work, current will continue to flow through the other path in the circuit and the other bulb will still light.
Source Switch Load #1 Parallel branches
Load #2
Ground
Ground
Troubleshooting Tip #2: An open circuit in a parallel branch prevents only the load in the open path from operating.
10
CIRCUIT REQUIREMENTS
Series-Parallel Circuits Besides series and parallel circuits, some vehicles also have series-parallel circuits. A seriesparallel circuit is a combination of the two circuit types. The parallel part of the circuit (load 1 and 2) can be diagnosed as a parallel circuit while the series part of the circuit (load 3) is diagnosed the same way as a series circuit.
Load #1 Switch
Load #2 Battery
Load #3 Dimmer Control (variable resistor)
Ground Ground
Series-parallel circuits typically contain a dropping resistor either before the circuit branches or in the ground side of the circuit after the loads. One common example of a series-parallel circuit is the dash light circuit. The dimmer control (variable resistor) is installed in series between the parallel loads (bulbs) and the circuit ground.
CIRCUIT REQUIREMENTS
11
In a parallel circuit, if the resistance of each bulb is the same, current flow will be the same. If resistance changes in any of the paths, current flow through that path will also change. A bad connection at one of the bulbs will change the resistance for only that one bulb. In the example below, high resistance causes load #2 to glow dimly, but load #1 operates normally. Vehicles use parallel circuits so each load has the same available voltage to operate it. These circuits typically branch out from the fuse box.
Load #1
Source
Switch
Load #2 Battery
Ground
Connection with high resistance
Ground
Troubleshooting Tip #3: An open in a parallel circuit only affects the operation of the load in the “open” branch. However, if a problem occurs before the circuit branches, it will affect both loads. If one or both loads operate poorly, look for high resistance in circuit connections.
12
CIRCUIT REQUIREMENTS
Circuit Protection Devices There are three types of circuit protection devices. They are fuses, fusible links and circuit breakers. Fuses, Fusible Links and Circuit Breakers Most electrical circuits use protection devices such as fuses, fusible links and circuit breakers. Circuit breakers open when excess current flow causes them to overheat. They reset after a cool-down period. Fuses and fusible links are thin wires that melt very easily when overheated by excessive current flow. Fuses and fusible links are built-in weak spots designed to protect circuit components and wiring from damage. Fuses fail because of two conditions: short circuits and grounded circuits. •
A crossover circuit (short to voltage) occurs when two different circuit conductors electrically touch each other. This occurs when a bare wire from one circuit touches a bare wire from another circuit. Such conditions may cause wiring to overheat or fuses to melt if the resulting current flow is greater than designed into either circuit. Normal circuit switching is no longer effective when this condition occurs. Conductor
Wire insulation
Short to voltage
Bare conductors touch and fuse melts to protect circuit
•
A short-to-ground occurs when current bypasses the circuit load and goes directly to ground. When this occurs, the resistance in the circuit is so low that current increases above the rating of the fuse protecting the circuit and the fuse melts. Never substitute a higher amperage rating fuse when this condition occurs because wiring will surely melt together as a result of higher than normal current flow. Conductor
Wire insulation
Short to ground Chassis Ground Bare conductor touches and fuse melts to protect circuit
CIRCUIT REQUIREMENTS
13
Fuses Fuse ratings are based on the current flow needed to operate the circuit while protecting it from excessive current flow. For example, a circuit that normally draws 6 amps might have a 10 amp fuse to protect it. If you replace one fuse with another that has a higher than recommended rating, a short circuit (resulting in excessive current flow) could damage circuit components before the fuse melts. Never substitute a fuse with a rating different than specified for that circuit. Refer to the label on the fuse panel for the correct application. Blade-type fuses have a high resistance to shock and vibration and greater durability once in service. The fuse material of blade fuses is molded into the colored plastic. The current rating is molded into the top of the fuse. The color also indicates the current rating.
Fuse Color
Current Rating
Brown
7.5 amps
Red
10 amps
Blue
15 amps
Yellow
20 amps
Green
30 amps
Fusible Links Fusible links also protect against excessive current flow. They protect circuits between the battery and the fuse block. Like fuses, fusible links use different colors to identify the amperage ratings of fusible links. The chart on the opposite page shows the common sizes. Troubleshooting Tip #4: Fuses and fusible links blow because of increased current flow (reduced resistance) in the circuit between SOURCE and GROUND.
14
CIRCUIT REQUIREMENTS
Color
Continuous Current Flow
Current to melt fusible link within 5 sec.
Brown
15 amps
About 120 amps
Green
20 amps
About 200 amps
Red
25 amps
About 250 amps
Black
33amps
About 300 amps
Fusible links: •
Protect high current, direct load circuits such as the radiator fan.
•
Provide current for multiple fused circuits (see illustration, next page).
•
Are only found on the source side of the circuit, never on the ground side.
Troubleshooting Tip #5: If an unwanted ground occurs on the GROUND side of the a LOAD in a ground-switched circuit, the LOAD will stay ON all the time. Troubleshooting Tip #6: Blown fuses often result after body or other major repairs to a vehicle. Always check for pinched wires in areas where repairs have recently been performed. Circuit Breakers Circuit breakers are circuit protection devices that open when excessive current flow causes them to overheat. The contacts close again after the circuit breaker cools down. Some circuits are equipped with circuit breakers that protect multiple circuits. See the power supply routing illustration that follows.
CIRCUIT REQUIREMENTS
15
Fusible links
Fuses
Circuit breaker protects multiple circuits
Note Note: Fuses and fusible links melt because of increased current flow (reduced resistance) in the circuit. Placing fusible links on the source side of a circuit will prevent wires from overheating.
16
CIRCUIT REQUIREMENTS
CIRCUIT CONTROLS So far, we’ve discussed circuit requirements (source, load and ground) and circuit arrangements (series, parallel and series-parallel). Electrical circuits are controlled by three different devices. They are: 1.
Switches
2.
Relays
3.
Electronic devices (such as the Engine Control Module). These will be covered later.
Switch-Controlled Circuits Even though the only requirements for a circuit to operate are a power, load and ground, most circuits are a little more complex. Switch-controlled circuits contain wires, connections, relays, motors, bulbs and a switch. Switches control either the source or ground side of the circuit. Some switches are manually operated. Some switches are temperature controlled, and yet others are controlled by pressure. No matter what type of switch is used, there are three important points to remember: 1.
Switches are not loads.
2.
Switches are wired in series with the circuit.
3.
Switches can be located on the source or the ground side of the load.
Troubleshooting Tip #7: If an entire circuit is dead, the problem is with a series component such as a switch or SOURCE, wiring connections, faulty load or the GROUND.
CIRCUIT CONTROLS
17
Switch Positions Switches are shown in wiring diagrams as if the vehicle is in the ¡°normal¡± condition. A vehicle is in the “normal” condition when: •
Ignition switch is OFF
•
Doors, hood and trunk lid/back door are closed
•
Pedals are not depressed, and
•
Parking brake is released
Normally Closed Switch (NC)
18
Normally Open Switch (NO)
CIRCUIT CONTROLS
The following switches are normally open (NO): Brake pedals (usually not depressed), doors (usually closed), hoods (usually down), parking brakes (usually released). The front door switches in the diagram below are “normally open” (NO) switches. When the doors are closed, both switches are open and the interior light is OFF. If the door switch contacts were to close (interior light ON) when the door closes, it would be classified as a “normally closed” (NC) switch.
Normally Open (NO) switches (manually switchable)
Door position
CIRCUIT CONTROLS
19
Multiple Position Switches Multiple position switches are similar to single contact switches. However, multiple switches connect more than one circuit so that separate devices (loads) can operate at the same time. For example, the wiper switch is a multiple switch. It can make different contact point connections to perform multiple functions. TURN Right turn FOG LAMP HEADLIGHT ON
OFF
N OFF
High beam
INT
WASH
ON Low beam
LO
OFF
Flash-to-pass
Left turn HI
The wiper switch has several positions—OFF, INT, LO, HI and WASH. These positions are listed across the top of the wiper switch chart that follows. The numbers along the left-hand side of this chart identify each of the terminals housed in the switch connector. These numbers are molded into the plastic housing of the wiper switch next to each of the switch terminals. Wiper Switch Chart Switch positions Switch terminal identification numbers
OFF Switch Open INT Intermittent (delay) LO Constant Low Speed HI Constant hight speed WASH Washers ON
Continuity points
The circles and interconnecting lines indicate the connections inside the switch. •
Circles show the internal connections in each switch position.
•
Line between the circles show terminal connections for each switch position.
Note Note: For example: In the LO switch position, only terminals #14 and #17 are connected or have continuity. 20
CIRCUIT CONTROLS
Wiper Switch Switch positions Switch terminal identification numbers
Continuity points
To understand the wiper switch circuit above, simply read down the column which identifies a particular switch position to see which terminals are connected by the circles and lines. Then read the corresponding circuit terminal numbers in the far left column. The shaded example shows terminals 14 and 17 connected when the switch is in the LO position. Using the above chart for reference, identify the connected terminals for the other switch positions:
Switch Position
CIRCUIT CONTROLS
Switch T erminals Terminals
OFF
and
INT
and
HI
and
WASH
and
21
ELECTRICAL TEST EQUIPMENT There are two categories of test meters available for automotive electrical testing: analog and digital. These categories refer to the type of meter display. The most common meter for automotive testing is actually three meters in one. It is called a digital multimeter (DMM). The three meters built into a multimeter are: •
Ohmmeter
Measures resistance ( )
•
Voltmeter
Measures voltage (V)
•
Ammeter
Measures current flow in amps (A)
Analog Meters Analog meters use a calibrated scale with a pointing needle to indicate the value of the measurement being made. The needle points to the position on the scale. Analog meters have serious limitations when used to test modern automotive computer-controlled circuits. Because of their low internal impedance (resistance), electronic control units may be damaged from increased current flow caused by connecting the meter in parallel. For this reason, they are not recommended for testing automotive electrical systems.
Analog Meter
Digital Meters Digital meters display a digital readout of the measurement being made. Use high impedance digital multimeters to test automotive electrical circuits. The more reliable digital multimeters have an input impedance of 10 megaohms or more.
22
ELECTRICAL TEST EQUIPMENT
Digital Multimeter (DMM) Safety Checklist: •
Use a meter that meets accepted safety standards.
•
Use a meter with fused current inputs. Be sure to check fuses before making current measurements.
•
Inspect test leads for physical damage before making a measurement.
•
Use the meter to check continuity of the tests leads.
•
Only use test leads that have shrouded connectors and finger guards.
•
Only use meters with recessed input jacks.
•
Select the proper function and range for the measurement you intend to make.
•
Be certain the meter is in good operating condition.
•
Follow all equipment safety precautions.
•
Always disconnect the red (+) test lead first.
•
Use a meter which has overload protection on the Ohms function.
•
When measuring current without a current amp clamp, turn the power OFF before connecting into the circuit.
•
Use extreme caution in high current and high voltage testing situations. Use the appropriate equipment, such as high voltage probes and high current clamps, for your personal safety.
Ohmmeter Use An ohmmeter has two important functions: •
Measuring circuit or component resistance.
•
Checking continuity in a circuit or a component.
Most ohmmeters have different measuring ranges. If you don’t know the resistance, start on the highest test scale first, then switch to a lower scale to obtain the most accurate reading. Most modern DMMs set the measurement range automatically (autorange).
ELECTRICAL TEST EQUIPMENT
23
CAUTION: NEVER USE AN OHMMETER ON A CIRCUIT WHILE IT IS OPERATING. THIS COULD DAMAGE THE METER. To use an ohmmeter: Step 1:
Set the meter to measure resistance (Ω).
Step 2:
Check meter calibration by touching the two test leads together. Typical test lead resistance is between 0.2 and 0.5 Ω.
Step 3:
Be sure the circuit being checked is switched OFF. Never use an ohmmeter on a circuit while it is operating. The ohmmeter has an internal battery. Additional voltage through the m eter may damage it if the meter does not have overload protection. Rotary switch
Step 4:
Connect the meter leads to the ends of the circuit or component to test and read the resistance.
Note Note: Take two (2) separate readings and compare them to determine how good the ground is. Non auto-ranging meters require you to multiply your reading based on the scale selected.
Sending unit
1st
2nd
For example:
24
ELECTRICAL TEST EQUIPMENT
Voltmeter Use A voltmeter is the most commonly used and most versatile of all automotive electrical testers. A voltmeter has two functions: •
Measuring circuit voltage
•
Measuring voltage drop
To measure voltage: Step 1:
Set the meter to measure voltage: DC (V ) or AC (V~). If circuit voltage is unknown, use the scale closest to, but higher than, 12 volts.
Step 2:
Connect the voltmeter probes in parallel across the circuit to obtain a voltage reading. Observe the polarity of the meter when making these connections. In other words, connect the red lead to the point closest to the battery and the black lead to the connection toward ground.
Step 3:
Operate the circuit being checked and read the voltage in the display window.
DC volts
Available Voltage Checking for available voltage measures the voltage available up to the location of the circuit to which the meter is connected. In a normal circuit, there should be source (battery) voltage available up to the load. Since the battery provides a constant 12 volts or more, any excessive resistance in the circuit will reduce the available voltage to operate the load. Reduced available voltage results in dim light bulbs, slower spinning motors and relay coil circuits that don't have enough “energy” to close the contacts. Troubleshooting Tip #8: You can also use a test light to test high current, NON-ELECTRONIC circuits. A test light can test bulb circuits, relay circuits and fuses for available voltage. However, a test light CANNOT measure the amount of available voltage, a decided disadvantage.
ELECTRICAL TEST EQUIPMENT
25
Voltage Drop Perhaps the biggest electrical problem faced by technicians is that of unwanted voltage drop in a circuit. All loads in a circuit have resistance and use voltage. However, voltage drop can also occur in other parts of a circuit, such as at connection points, and this can affect circuit operation. A voltage drop test is a way of measuring the voltage used by an individual circuit load or connections within the circuit. The voltage drop measurement tells you how much voltage is used between the meter test leads. Rule of Thumb for Voltage Drops at Connections Note Note: Maximum allowable voltage drops: Wire Connections less than 0.1 Volts Ground Connections 0.1 Volts Switch Contacts 0.3 Volts Starter Solenoids 0.5 Volts Each resistance in a circuit uses voltage, so a voltmeter can isolate circuit malfunctions by measuring the voltage drop in a selected part of the circuit. Earlier, we said that a switch is not a load. However, during diagnosis, use a voltmeter to measure voltage at each of the switch contacts. This will indicate whether the switch is making and breaking contact as it should. A voltage drop across the closed contacts indicates excessive resistance and will cause the circuit to operate incorrectly. Troubleshooting Tip #9: The greater the resistance in any part of a circuit, the greater the voltage drop.
26
ELECTRICAL TEST EQUIPMENT
Look at the wiring in this drawing. If an ohmmeter were connected as shown, the single strand of wire still making contact would give an ohmmeter reading of near 0 (zero) ohms (no resistance) indicating a good circuit. However, during circuit operation this single strand of wire cannot carry the amperes necessary for the circuit to operate properly. While the ohmmeter's low resistance gives the indication that there is continuity, the single strand of wire impedes current flow. Therefore, a voltage drop occurs at this point in the circuit.
Important Note: Unwanted resistance can take many forms. For example, water can cause corrosion inside a wire connector. This creates excessive resistance that reads on the voltmeter as a voltage drop. Likewise, dirty or corroded switch contacts and loose wire connections can produce unwanted resistance and cause a voltage drop. Troubleshooting Tip #10: When isolating circuit problems, perform tests that: - You can do quickly - You can do easily - Tell you most about the problem
ELECTRICAL TEST EQUIPMENT
27
Inline Voltage Drop To measure voltage drop:
V
V
V V
Switch
V Battery (source)
Excessive Vdrop V
Connection with a high resistance
a=b+c+d+e+f Step 1:
Connect the voltmeter across the connection or portion of the circuit to be tested. The positive lead of the voltmeter should be close to source and the negative lead close to ground.
Step 2:
Operate the circuit.
Step 3:
The voltmeter will indicate how many volts are used by that part of the circuit.
Voltage drop can occur in any part of a circuit. Because a circuit must have source, load and ground to operate, check the ground side of a load for voltage drop as well. Look for bad ground connections at the vehicle frame, corrosion at the negative post of the battery and loose ground straps or connections at components such as the starter motor and alternator.
28
ELECTRICAL TEST EQUIPMENT
Ammeter Use An ammeter measures current flow in a circuit. If specifications are available, amperage (current) readings can be helpful during diagnosis. Starter current draw (amperage) readings are listed in the Service Data and Specifications of the service manual. However, amperage specifications are not available for most other electrical circuits. To measure current: Step 1:
Connect the ammeter in series in the circuit. This means that all the current flowing in the circuit will flow through the meter. Some hand-held meters can only measure up to 2 amps. Some meters have the capability to measure up to 10 amps. CAUTION:
THE AMMETER IS NOW PART OF THE CIRCUIT AND EXCESSIVE AMPERAGE, SUCH AS MIGHT OCCUR IN A SHORT CIRCUIT, CAN DAMAGE THE AMMETER FUSE. ALWAYS CHECK FUSES ACCORDING TO THE METER INSTRUCTIONS. Step 2:
Be sure the positive lead of the ammeter is toward the battery plus (+) terminal and the negative ammeter lead connects to the ground or negative (–) side of the circuit.
Step 3:
Switch the circuit ON. An amperage reading above specifications indicates low circuit resistance. A lower than normal current reading could be caused by a weak battery, defective charging system or high circuit resistance.
Note Note: Many ammeters have an inductive pickup instead of separate ammeter leads. Inductive ammeters are both accurate and easy to use without becoming a part of the circuit.
A
Ammeter reads circuit current Load
Battery
ELECTRICAL TEST EQUIPMENT
Connect ammeter to circuit at fuse or switch to measure total circuit current
29
Kent-Moore J-44373 Model 620 Tester This tester is used to test batteries, starters and charging systems. It uses the conductance method to determine the battery's ability to produce voltage. Conductance is a measure of the plate surface available in the battery to determine how much voltage the battery can produce. To determine the battery conductance, the tester produces a small signal which is sent through the battery. The tester then measures a portion of the AC current response. The tester can test a battery exactly as received without having to recharge it before testing. Because no loads are applied to the battery, the test is completely safe. The results provide a good indication of the battery condition based on the results in the chart below. In some cases, the tester may recommend a charge and retest. WARNING: NEVER RECHARGE A BATTERY IF THE TESTER INDICATES THERE ARE BAD CELLS. DOING SO COULD CAUSE THE BATTERY TO EXPLODE AND INJURE YOU AND/OR ANYONE NEARBY.
J-44373 T est Results Test Battery T ests Tests
Starter T ests Tests
Charging System T ests Tests
•
Good battery
•
Cranking voltage normal
•
•
Good, but needs recharge
•
Cranking voltage low (starter suspected)
Charging system diode ripple normal
•
•
Fully charge battery, then retest
•
Charging system incident caused by:
•
Replace battery and retest
•
Bad cell detected
•
Charge battery (insufficient charge for test) Replace battery
- No charging voltage - Low charging voltage - High charging voltage - Excess ripple detected
Note Note: • •
30
Record output codes for each test on the work order. Record date and time before performing tests.
ELECTRICAL TEST EQUIPMENT
Relay Controlled Circuits Relays are used to connect two parts of a circuit, much like a switch, by using low amperage (thin) wires to control a higher amp circuit. However, a relay is not operated mechanically like the other switches we discussed. Inside the relay housing there are two circuits: the control circuit and the contact circuit. The control circuit contains a coil of fine wire which, when energized, develops a magnetic field. The contact circuit contains a spring-loaded switch arm that connects the relay contacts when the control circuit is energized. The magnetic field pulls the contacts closed. Relays have two separate circuits: •
Coil control (low current) circuit
•
Contact (high current) circuit Source
Source voltage to high current circuit
Relay housing Contact circuit (high current), not yet connected
Control circuit (low current)
Ground through ECM or external switch
ELECTRICAL TEST EQUIPMENT
To circuit load
31
Like switches, relays can have normally open (NO) or normally closed (NC) contacts. In wiring diagrams, hollow circles represent normally open relay contacts. Darkened circles represent normally closed relay contacts. Refer to the following chart for more details. NO and NC Relays
Not Energized Does not flow
Energized Flows
Normally Open (NO) Relay
Switch 1
Battery
Switch 1
Battery
Does not flow
Flows
Normally Closed (NC) Relay
Switch 1
Battery
Switch 1
Battery
Some relays have a single contact point circuit and others have two. Some relays have only normally open contacts, while others have a combination of normally open and normally closed contacts. The circuit design dictates the type of relay to use.
32
ELECTRICAL TEST EQUIPMENT
There are four types of relays used on vehicles: 1.
1M
(One-Make Relay)
2.
1T
(One-Transfer Relay)
3.
2M
(Two-Make Relay)
4.
1M-1B (One-Make, One-Break Relay)
To identify the connections used with each of the relays, a small diagram showing each of the terminal numbers is molded into the top of the relay. On the bottom of each relay, terminal numbers are shown next to each terminal.
ELECTRICAL TEST EQUIPMENT
33
1M (One-Make) Relay Operation The “1M” relay has four terminals in a single connector. Relays of this type are enclosed in either a blue, green or yellow housing depending on the amperage rating of the contact point circuit. The green relay is normally found on a ground circuit. Wire terminals #1 and #2 of the 1M relay connect the coil to an external control. When current flows through this circuit, a magnetic field develops causing the contacts between terminals #3 and #5 to close. This high current circuit connects the load to source or ground to complete the circuit.
1-M Relay and Symbols Used
Bottom view
Color Code: Blue, Green or Y ellow Yellow
Circuit diagram
Wiring diagram
Troubleshooting Tip #11: Although the configuration of the blue, green and yellow relays is the same, do not interchange them. They have different operating specifications.
34
ELECTRICAL TEST EQUIPMENT
Relays plug into wire connectors or relay sockets. The service manual identifies each relay socket with a connector number. In the following fog lamp relay circuit, the connector number is E49. In the following wiring diagram: •
The P/L (pink with blue stripe) wire (terminal #1) and the G/OR (green with orange stripe) wire (terminal #2) are connected to the coil control circuit.
•
The OR (orange) wire (terminal #3) and the OR/B (orange with black stripe) wire (terminal #5) are connected to the contact circuit.
Relay and relay socket connector number
E49
1M Relay
ELECTRICAL TEST EQUIPMENT
35
1T (One Transfer) Relay Operation The 1T relay has a black housing with five wire terminals. It operates like the 1M type relays with one exception. There is normally contact between terminals #3 and #4 until the relay is energized. When energized, current then flows from terminal #3 through terminal #5.
1T Relay and Symbols Used 1-T
Bottom view
36
Color Code: Black
Circuit diagram
Wiring diagram
ELECTRICAL TEST EQUIPMENT
1T Relay
1T Relay
ELECTRICAL TEST EQUIPMENT
37
2M (Two-Make Relay) Relay Operation The 2M relay has a brown housing and is similar to the 1M type relay. However, the 2M relay completes two separate circuits when the coil control circuit is energized. Terminals #3 and #5 connect one circuit and terminals #6 and #7 connect the other. 2M relays are used to divide current flow through two sets of contact points when high current flow may burn the contacts in a 1M relay.
2-M Relay and Symbols Used
Bottom view
Color Code: Brown
Circuit diagram
Wiring diagram
A malfunction with a 2M relay can: •
Prevent both loads from operating if the malfunction occurs in the coil control circuit.
•
Prevent one of the loads from operating if the malfunction occurs in either of the contact point circuits.
38
ELECTRICAL TEST EQUIPMENT
In the following Rear Window Defogger circuit, two sets of contacts close at the same time when the coil control circuit is energized. This provides two current paths to the rear window defogger.
2M Relay
2M Relay
ELECTRICAL TEST EQUIPMENT
39
1M-1B (One-Make, One-Break) Relay Operation The fourth type of relay, housed in a gray case, is the 1M-1B type relay. When the coil control circuit of a 1M-1B relay is not energized, continuity exists through the normally closed contact point circuit between terminals #3 and #4. When the coil control circuit between terminals #1 and #2 is energized, the circuit connecting terminals #3 and #4 opens. At the same time, the normally open contact point circuit between terminals #6 and #7 closes, allowing current to flow.
1M-1B Relay and Symbols Used
Bottom view
Color Code: Gray
Circuit diagram
Wiring diagram
If the coil control circuit fails: •
the normally closed circuit connecting terminal #3 to #4 will not open.
•
the normally open circuit between terminal #6 and #7 will not close.
40
ELECTRICAL TEST EQUIPMENT
In the following circuit, the inhibitor switch must be either in ¡°P¡± or ¡°N¡± to complete the ground for the coil control circuit. This would then connect the contacts between terminal #6 and #7 allowing the engine to start.
1M-1B Relay
This circuit must be energized to start engine
1M-1B Relay
ELECTRICAL TEST EQUIPMENT
41
METER AND GAUGE SYSTEM System Operation Overview Automotive gauges display temperature, pressure or quantity. Most Nissan and Infiniti vehicles use “needle type” gauges. Instrument gauges activate when the ignition is switched ON. Needle-type gauges contain a circuit that consists of a coil of wire connected in series to a sending unit, which is attached to the object to measure. The sending unit is a resistor. Its resistance changes according to what the gauge is designed to monitor (oil pressure, coolant temperature, fuel level, etc.). For example, in a temperature gauge, when the engine temperature is high, the resistance in the sending unit (and the circuit) is low. The voltage in a variable resistance circuit changes the magnetic field in the gauge coil, which changes the position of the needle pointer. The scale in the gauge is calibrated to the movement of the gauge needle.
Gauge sending units
1
2 2
1. Thermistor 2. V ariable resistor Variable
42
METER AND GAUGE SYSTEM
In the previous illustration, the tachometer, speedometer, fuel gauge and water temperature gauge receive battery voltage with the ignition switch in the ON or START position. Voltage is supplied through terminals #41, #10 and #22 to the speedometer, tachometer, water temperature and fuel gauges. The other combination meter terminals connect to ground and gauge sensors or transmitters. For example, terminal #42 connects to the thermal transmitter to sense coolant temperature. Terminal #14 connects to the fuel tank gauge unit to sense fuel level in the gas tank.
Speedometer Operation The speedometer receives an alternating current (AC) signal from a vehicle speed sensor. The vehicle speed sensor is attached to the drivetrain (transaxle/transmission). It mechanically transmits the AC signal through terminals #24 and #30 at the combination meter (see the previous illustration, ELTC1-46, page 36). Speed Sensor
Speed Sensor Pinion
The AC signal is an analog signal (also called a sine wave). The voltage is measured continuously in one second intervals. The number of complete sine waves produced in one second is called the number of cycles-per-second or the number of Hertz (Hz). Hertz applies to the frequency of any repetitive signal. The vehicle speed sensor signals are also sent to the ECM, automatic transmission control unit and ASCD control unit by way of the speedometer.
METER AND GAUGE SYSTEM
43
MOTORS Motors are electromagnetic devices and have many applications. You’re probably most familiar with the starter motor. Smaller motors operate windshield wipers, electric windows, power seats, sunroofs, power antennas, and fuel pumps. When current is applied to a motor, it creates two magnetic fields. The field coils are constant: one is always north, the other always south. However, the magnetic field in the armature switches so the attraction/repulsion effect of the armature’s magnetic field will cause the armature to spin. Repulsion of two north poles, for example, “pushes” the armature about a quarter turn. Then the attraction of a north and south pole “pulls” the armature an additional quarter turn to maintain the momentum of the motor.
To match the motor to the operating requirements of the system, many windings of wire are wrapped around the field shoes and armature. The number of windings determines the speed and torque of the motor. Some motors, such as window and sunroof motors, need to rotate in two directions. Changing the direction a motor rotates involves using a switch to change the polarity from positive (+) (voltage), to negative (–) (ground) to the motor.. Troubleshooting Tip #12: When diagnosing motor circuits, directional control of the motor is important. If one brush is direct to SOURCE or GROUND, the motor runs in one direction.
44
MOTORS
STARTING SYSTEM Typical Automatic T ransmission-Equipped V ehicle: Transmission-Equipped Vehicle: The starting system cranks the engine when starting. The starting system consists of the: • starter motor • ignition switch • park/neutral position relay • park/neutral position switch • related fuse • fusible link • wiring and connections For the starter to operate, a 40A fusible link to the ignition switch supplies source voltage from the battery at all times. With the ignition switch in the ON or START position, a 15A fuse to the park/neutral position relay supplies source voltage. In addition, with the ignition switch in the START position, the ignition switch supplies source voltage to the park/neutral position relay. The circuit is grounded when the selector lever is in either the P or N position. The park/neutral position relay is energized by power supplied from the ignition switch, through the park/neutral position relay to the starter motor windings. When this circuit is complete, the starter motor plunger closes, providing a complete circuit between the battery and the starter motor. The starter motor is grounded to the cylinder block. With source voltage and ground supplied, the starter motor operates.
STARTING SYSTEM
45
Starting System: V ehicles with A/T Vehicles
46
STARTING SYSTEM
Typical Manual T ransmission-Equipped V ehicle: Transmission-Equipped Vehicle: On manual transmission-equipped models, the starting system consists of the starter motor, ignition switch, clutch interlock relay, clutch interlock switch, related fuse, fusible link, wiring and connections. For the starter to operate, source voltage a 40A fusible link supplies at all times to the ignition switch. With the ignition switch in the START position, source voltage is supplied through the ignition switch to the clutch interlock relay. In addition, with the ignition switch in the START position, a 10A fuse supplies source voltage to the clutch interlock relay. While you hold the clutch pedal depressed, ground is supplied to the clutch interlock relay through the clutch interlock switch and accompanying body grounds. The clutch interlock relay is then energized and source is supplied from the clutch interlock relay to the starter motor windings. The starter motor plunger closes and provides a closed circuit between the battery and the starter motor. The starter motor is grounded to the cylinder block. With source and ground supplied, the starter motor operates. Starting System Diagnosis & Repair Procedure Note: If a starting system failure is indicated, you must complete visual inspections and voltage drop tests before replacing the starter. Follow these steps to ensure that other possible causes are ruled out first. 1.
Confirm starting system failure symptom by attempting to start the engine.
2.
Check condition of all fuses and fusible links connected to the starting system circuit.
3.
Check condition of all accessible harness connectors connected to the starting system circuit.
4.
Ensure the vehicle has a fully charged battery that meets vehicle specifications installed.
5.
Ensure engine mechanical condition is good. A vehicle that exhibits extended cranking symptoms may cause additional strain on the starting system. This could possibly result in starter failure.
6.
Test starting system using Kent-Moore J44373 Battery, Starter, Charging System tester.
7.
If a starting system failure is indicated, perform voltage drop tests on the starting system before replacing the starter. Perform voltage drop tests while cranking the engine.
8.
Compare your readings with the known good readings shown in the graphics on the following pages. If your readings do not agree with these readings, check a known good vehicle with the same engine as the one you are testing.
STARTING SYSTEM
47
Starting System: V ehicles with M/T Vehicles
48
STARTING SYSTEM
CHARGING SYSTEM DESCRIPTION The charging system provides DC voltage to operate the vehicle’s electrical systems and to keep the battery charged. It consists of the alternator, ignition switch, charge indicator lamp in the combination meter and related fuse, fusible link, wiring and connections. The IC regulator controls alternator output voltage at the S terminal. For the alternator to charge, a 120A fusible link and a 10A fuse supplies power at all times to terminal S. Terminal B supplies power to charge the battery and operate the vehicle’s electrical system. The alternator is grounded to the engine block. With the ignition switch in the ON or START position, a 10A fuse supplies source to the combination meter for the charge warning lamp. Ground is supplied to the combination meter through terminal L of the alternator. With source and ground supplied, the charge warning lamp will illuminate. When the alternator is producing sufficient voltage with the engine running, the ground is opened and the “charge” warning lamp will go off. If the charge warning lamp illuminates with the engine running, a fault is indicated. Charging System Diagnosis & Repair Procedure Note: If a charging system failure is indicated, complete visual inspections and voltage drop tests before replacing the alternator. Follow these steps to ensure that other possible causes are ruled out first. 1.
Check the condition of all fuses and fusible links connected to the charging system circuit.
2.
Check condition of all accessible harness connectors connected to the charging system circuit.
3.
Check condition and tension of the alternator drive belt.
4.
Ensure the vehicle has a fully charged battery that meets vehicle specifications installed.
5.
Ensure that engine mechanical condition is good. Any vehicle that exhibits extended cranking symptoms may cause additional strain on the charging system. This could result in alternator failure.
6.
With the ignition ON, engine OFF, confirm the “Charge” lamp is ON.
Note: If the Charge lamp is not on, diagnose this problem first. The charging system will not work if the charge lamp is not working. 7.
Confirm charging system failure using Kent-Moore J44373 Battery, Starter, Charging System tester.
8.
Perform voltage drop tests of the charging system circuits with the engine running at a constant 1500-RPM. Load the alternator by turning headlamps and rear window defogger ON.
CHARGING SYSTEM DESCRIPTION
49
Charging System
50
CHARGING SYSTEM
ELECTRICAL DIAGRAMS Service literature uses two types of diagrams to help interpret and trace the wiring on vehicles: •
Schematic Diagrams
•
Wiring Diagrams
Schematic Diagrams The schematic diagram is a simplified electrical diagram of a circuit. This example of a turn signal and hazard warning lamps circuit shows all the main components of the circuit. This makes it easy to find source, load and ground on one page. However, the diagram does not show important repair details such as connector numbers, wire color codes and fuse identification and location. For that you need a wiring diagram. Wiring Diagrams
ELECTRICAL DIAGRAMS
51
Wiring Diagrams provide a road map of electrical circuits and contain more detail than schematic diagrams. They show: •
Connector types and color
•
Wire colors
•
Wire position in the connector
•
Connector numbers (for location)
•
Location of wiring harness on the car
•
Fuse ratings
•
Accessory wiring harnesses
•
Number of pin receptacles in a connector
•
Splices in a circuit
•
Ground locations
Wiring diagrams provide a detailed view of a system. This can help isolate individual circuits for testing. The ability to follow and interpret electrical diagrams is essential to diagnose and repair electrical circuit malfunctions. Wiring diagrams contain many important abbreviations, symbols, identifiers and codes. The follow example describes these important features. Recognizing them and knowing what they mean will help you use wiring diagrams more effectively when diagnosing and repairing electrical malfunctions. Troubleshooting Tip #13: Though a wiring diagram may show only one wire in a connector, there may be more. Other wires will not appear when they are part of different, unrelated circuits.
52
ELECTRICAL DIAGRAMS
The example wiring diagram below shows: •
R/L is a Red wire with a blue stripe which connects terminal 12 of the combination switch and terminal 12S of the fuse block.
•
Fuse block terminal 11S connects to both front side marker lamp assemblies.
•
Fuse block terminal 10Q connects to the taillamp circuit shown on the next page of the repair manual.
Electrical wiring diagrams divide the entire electrical system into individual circuits. Thus, a typical wiring diagram shows one circuit from battery to ground. Wiring and components that are not part of the individual circuit are cross-referenced at connection points.
Tail lamp circuit continues on next page
ELECTRICAL DIAGRAMS
53
These wiring diagrams are easy to read and trace because the source (battery) is always at the top of the page and the ground connections are always at the bottom of the page (as if current flows down hill). Components, wires, switches, lamps and fuses are shown as simply as possible. For example, a wire that is 6 feet in length on the vehicle may be shown no differently than one that is 6 inches long. The General Information (GI) section in the service manual describes how to read the new style wiring diagrams. Review the sample diagram Graphical Wiring Diagram in this section as well as the accompanying explanations of the lines and symbols. The Electrical (EL) section of newer service manuals contains the following types of diagnostic information: •
Wiring diagrams diagrams, which show the electrical current path when the circuit is operating properly. It is essential to understand how a circuit should operate before attempting to diagnose a malfunction.
•
System descriptions descriptions, which describe how current flows through the system from the source to the ground.
•
Component part locations locations, which show a picture of where the component is actually located on the vehicle.
•
Harness layout and connector locations locations, which are found toward the back of the EL section.
•
Diagnostic procedures procedures, which provide a step by step diagnostic procedure based on the malfunction symptom.
Example: To review how the Meter and Gauge circuit operates, turn to the Meters and Gauges System Description in the EL section of the service manual. Read the System Description and analyze the wiring diagram(s) to get a basic understanding of how the circuits operate. After learning how the circuit should operate, perform basic visual inspections and checks for available voltage and ground. This is important because many diagnostic procedures assume you have checked for voltage and ground before performing further diagnostic procedures.
54
ELECTRICAL DIAGRAMS
Connector Symbols in Electrical Diagrams In order to diagnose and repair electrical malfunctions, you must understand how to read and interpret wiring diagrams. The wiring diagram includes all the details of how the circuit is actually wired on the vehicle. The wiring diagram includes all connectors, wire colors, fuse locations and connector reference locations. In this vehicle wiring diagram the horn relay connects to the engine harness at E37. To further isolate the location of this connector, refer to the Harness Layout Diagram in the EL section of the service manual.
Horn Relay and Connector E37
Typical switch details
Typical ground symbol
ELECTRICAL DIAGRAMS
55
Since electrical diagrams include a lot of information on a single page, accurate tracing of a single circuit is not always easy. Remember these important points when you use the diagrams: •
The two halves of a connector fold like a book.
•
Wires sometimes change colors from one side of a wire connector to the other side.
•
All connector symbols in wiring diagrams are viewed from the terminal side, unless otherwise noted.
•
Only the wires that are part of the circuit are shown in the connector.
•
If the plastic connector is female, the terminals inside are male, and vice versa.
As there are six cavities, the connector has up to six terminals Black print shows that it houses a male terminal (metal part not plastic) A chamfered corner shows that it is a pin-type terminal A right-angled corner means that it is a flat or spade terminal
Connector with pin terminals
Symbol Since it is white here, it is a female terminal (metal part) There are eight cavities, so the connector has up to eight spade terminals
Connector with spade terminals
Note Note: Though a wiring diagram may show only one wire in a connector, there may be more. Other wires will not be shown when they are part of different, unrelated circuits.
56
ELECTRICAL DIAGRAMS
•
Connector guides for male terminals have a black mark on the connector symbol. Connector guides for female terminals have a white or hollow area on the connector symbol. Male T erminal Terminal
Symbol
Guide
Actual connector
Number of cavities
Number of terminals available
Black print
Male terminal
White print
Female terminal
Chamfered corner
Pin-type connector (bullet)
Right-angled corner
Spade terminal
Connector symbol
Connector
Female T erminal Terminal
Guide
Connector symbol
Connector
Refer to a component’s wiring diagram to determine the number of wires, type of connector and whether it is male or female. Note Note: An “X” in a wiring diagram wire connector means there is no terminal in that connector cavity. no terminal
X Connector symbol
ELECTRICAL DIAGRAMS
57
Connector Direction Marks A direction mark symbol is used to differentiate between the harness side of the connector and the terminal side of the connector. These marks represent the side of the connector which should be tested.
View from terminal side (TS)
View from harness side (HS)
All connector symbols shown from the terminal side are enclosed by a single line, and connector symbols shown from the harness side are enclosed by double lines. Connector symbols
Double line
Single line
View from terminal side
View from harness side
Each connector symbol also includes a guide for the connectors. If the guide is not filled in, the wire terminals are female. If the guide is black, the wire terminals are male. In addition, the troubleshooting guide flow charts use symbols to indicate whether a test should be performed with the connector connected or disconnected, as well as many other testing conditions that must be met.
58
ELECTRICAL DIAGRAMS
Wire Color Code A standard color code has a one or two letter code (e.g. “R, W, B or BR”). If a wire has a two letter code separated by a slash (e.g. “R/W” or “G/Y”), the first letter represents the standard color and the second letter represents the supplementary (stripe) color. The standard color for “grounding circuits” is black. Wires connected to some components may also be black. Black wires are not always ground wires. If the wire insulation color is striped, the base color is given first, followed by the stripe color. Example: L/W = Blue with White Stripe
Wire Color Code Chart B
= Black
BR
= Brown
W
= White
OR or O
= Orange
R
= Red
P
= Pink
G
= Green
GY or GR
= Gray
L
= Blue
PU or V
= Purple
Y
= Yellow
SB
= Sky Blue
LG
= Light Green
CH
= Dark Brown
DG
= Dark Green
Wire Gauge Wire gauge describes the diameter of wire conductors. As the wire gauge number gets larger, wire diameter gets smaller. Large gauge wire has greater current-carrying capacity. For example, a 10 gauge wire conductor is thicker than a 14 gauge wire and can carry up to 24 amps while the 14 gauge wire can carry a maximum of 14 amps.
Insulation
Conductor
10 gauge wire compared with 18 gauge wire
ELECTRICAL DIAGRAMS
59
Wiring Repairs Nissan and Infiniti provide wiring harnesses and most electrical components as repair parts. An electrical terminal kit with an assortment of electrical terminals and terminal remover tools is available for minor wiring harness repairs. When working on wiring harnesses, always use the appropriate terminal removal tool. Using the proper tool reduces damage to the wire terminals and connectors. Solder terminals and cover exposed wires with shrink wrap. Note Note: When repairing electrical wiring, always use the correct wire size and avoid using solderless terminals.
Connection Repair Kit
Wire Connectors Harness connectors are designed to stay tightly connected. To separate these connectors, push or lift a special locking section of the connector. Never pull the wire harness when separating connectors.
Terminal retainer Push
waterproof seal
Terminal retainer Lift
In spite of the locking design, connectors sometimes become loose or disconnected. Attempt to pull the two connector halves apart to verify they are making good contact. When separating a connector, be sure the waterproof seal is in place when you reconnect it. Look for signs of corrosion or discoloration that can cause increased resistance, which leads to unwanted voltage drop.
Push
Push
Push (for combination meter)
Push
Push
Push
(for relay)
Disconnecting, inspecting, and reconnecting wire connectors in a non-functioning circuit will often return the circuit to operation. The act of separating and reconnecting the connector cleans and reseats the connector terminals.
60
ELECTRICAL DIAGRAMS
Trouble Diagnosis Charts Troubleshooting guides for many systems are also included in the EL section of the service manual. They are a valuable source of information to solve circuit malfunctions. The chart is divided into three columns to help pinpoint the cause of the circuit malfunction. The circuit wiring diagram accompanies the Trouble Diagnosis Chart. Symbols are used to identify the tasks to be performed. Note Note: Follow the chart completely. Do not skip around. Perform each test before going on to the next. Be sure you know what each test is telling you. You should have a good idea what part of the circuit is being checked and the results a good component will give.
Harness Connector I.D.
Note terminal location in male/female connectors
Circuit Wiring Diagram
ELECTRICAL DIAGRAMS
Circuit Diagnostic Flowchart
61
Trouble Diagnosis Charts contain symbols which are identified by a number. A description of each symbol and number follows. a
ohmmeter An _______________ is used to check continuity.
b
ignition switch is “OFF”. The _________________
c
wire connector The __________________ is disconnected.
d
ground One lead of the ohmmeter is connected to _____________.
e
connector number E14 is the _____________________.
f
Male _________ terminals inside connector.
g
terminal Perform the test at _______________ #33.
h
harness side of connector E14. Perform the test on the _______________
i
tested The wire connector is viewed and ____________ from the harness side.
8
6
A
9
Disconnect
33
2
3 5 7
E14 1
4
Note Note: All test conditions must be met if you want accurate results.
62
ELECTRICAL DIAGRAMS
Key to Electrical Symbols
ELECTRICAL DIAGRAMS
63
Harness Layout Diagrams Harness Layout diagrams describe the locations of all connectors of a specific harness as they appear on the vehicle. In addition, these diagrams show ground locations and some of the major components that connect to the harness. This layout for the taillight harness shows the location of each connector. Verify the correctness of the connector location by matching wire colors and number of wires prior to performing tests.
Taillight Wiring Diagram Locate harness connectors using layout diagrams
Connector numbers
Harness Layout Diagram: Tail Harness
64
ELECTRICAL DIAGRAMS
Location of Electrical Units The EL section of the service manual shows the location of major electrical components in the segment labeled Location of Electrical Units. Both under-hood and interior locations are described. The location of components description is approximate and may change depending on installed accessories and available options. LOCA TION OF ELECTRICAL UNITS OCATION Passenger Compartment
Troubleshooting Tip #14: After tracing a circuit with the wiring diagram, use the Location of Electrical Units section to locate test points that are easy to find and will help isolate the problem.
ELECTRICAL DIAGRAMS
65
Foldout Circuit Diagrams The foldout pages at the back of some service manuals contain valuable information for diagnosing circuit malfunctions. Information contained in these foldout pages varies depending on the year of the service manual. Service manuals produced before the 1994-95 Model Year contain different electrical information than manuals produced after those years. There are two types of foldout pages used in service manuals: 1.
Foldout Circuit Diagrams used in 1994 and older service manuals.
Service manuals produced before 1994 use foldout pages that contain circuit diagrams of the entire vehicle. These foldout circuit diagrams separate the electrical system into three levels. Each level has power at the top, the circuit load in the middle and ground at the bottom. Analyzing a circuit in this format helps to eliminate the clutter of wires, components and connectors. Use the foldout circuit diagram to determine what components of other circuits interconnect with the circuit you’re tracing.
66
ELECTRICAL DIAGRAMS
2.
Foldout Circuit Diagrams used in 1995 and later service manuals.
1995 and newer service manuals have foldout pages that contain detailed connector and terminal location information for these items: •
Super Multiple Junction (SMJ)
•
Hybrid Electrical Connector (HEC)
•
Fuse and Fusible Link Box and the Junction Box.
Examine the following sample foldout page. Notice how the reference area on the starting system wiring diagram page is linked to the SMJ terminal arrangement foldout page. This is helpful when trying to locate a terminal for testing.
ELECTRICAL DIAGRAMS
67
Power Supply Routing Schematic This is a schematic diagram that identifies all the system fuses and the different circuits that are powered by each fuse. Use this chart to identify and locate the available voltage for a circuit.
Multi-Remote control relay A/C relay Clutch interlock relay (M/T models) Inhibitor relay (A/T models)
Cooling fan relay-1 Horn relay
Front fog lamp relay Theft warning relay Theft warning lamp relay Cooling fan relay-3 Horn relay-2 Cooling fan relay-2
68
ELECTRICAL DIAGRAMS
Ground Distribution Chart These charts identify all the electrical system ground connections, connector numbers and wiring diagrams for each circuit. When a system ground is suspected as being faulty, this chart can identify the ground connector and the various circuits shared by common grounds. Circuit description
Ground connection location
Circuit Identification in service manual
Load connector number
200SX/Sentra service manual: Answer the following questions in regard to the1997 __________________ 1.
EL -102 EL-102 What page in the service manual page contains the brake fluid level circuit? ________
2.
Where in the vehicle is the ground connection (E13/E25) for this circuit? Behind left front headlight _______________________
3.
What page in the service manual page contains the Harness Layout chart for this circuit? EL -236 EL-236 ___ ______
4.
What are the coordinates on the Harness Layout that identify the location of the Brake Fluid E-2 Level Switch connector (E1)? __________
ELECTRICAL DIAGRAMS
69
Using the Service Manual to Research Related Information Now that you are familiar with the layout of the electrical (EL) section of the service manual and learned how to interpret information, imagine you’re in a situation where you need to thoroughly research a circuit. You might look for related circuit information like component locations, power feeds, SMJ connectors, electrical units, joint connectors or ground locations. The following pages are similar to how you might research them in a diagnostic situation. By gathering these pages, you should be able to better understand how various components are related. The following pages are related to the horn circuit on a 2001 model Maxima. When conducting research of your own, you might find it useful to have pages such as these to help you diagnose a particular circuit fault. Use this as a reference until you feel comfortable locating the different sections of the manual on your own.
70
ELECTRICAL DIAGRAMS
HORN
Engine harness
See engine room harness (ground distribution)
ELECTRICAL DIAGRAMS
71
VEHICLE SECURITY (THEFT WARNING) SYSTEM
72
ELECTRICAL DIAGRAMS
Horn circuit (power supply) fuses
POWER SUPPLY ROUTING
ELECTRICAL DIAGRAMS
73
POWER SUPPLY ROUTING
74
ELECTRICAL DIAGRAMS
POWER SUPPLY ROUTING
ELECTRICAL DIAGRAMS
75
HARNESS LAYOUT Outline
76
ELECTRICAL DIAGRAMS
HARNESS LAYOUT How to Read Harness Layout
ELECTRICAL DIAGRAMS
77
HARNESS LAYOUT Engine Room Harness
78
ELECTRICAL DIAGRAMS
HARNESS LAYOUT
ELECTRICAL DIAGRAMS
79
GROUND Engine Room Harness
80
ELECTRICAL DIAGRAMS
GROUND
ELECTRICAL DIAGRAMS
81
ELECTRICAL UNITS LOCATION Engine Compartment
82
ELECTRICAL DIAGRAMS
ELECTRICAL UNITS LOCATION Passenger Compartment
ELECTRICAL DIAGRAMS
83
ELECTRICAL UNITS LOCATION
84
ELECTRICAL DIAGRAMS
ELECTRICAL UNITS LOCATION
ELECTRICAL DIAGRAMS
85
ELECTRONICALLY CONTROLLED CIRCUITS The last category of vehicle circuits found on vehicles is called electronically controlled circuits. These circuits use an Electronic Control Unit (ECU) with various inputs and outputs. These ECUs are sometimes called amplifier or timer circuits. For example, an A/C Auto Amp controls air conditioning compressor operation; an automatic temperature control (ATC) head is called an auto amplifier; a door lock timer controls power door lock operation.
Operation Electronic circuits are unique because an ECU uses internal logic, circuitry and memory to control circuit operation. Relay and switch circuits do not have these capabilities. Electronically controlled circuits require: •
Input - Sensors provide electrical signals to the ECU.
•
Logic - Processing of input signals to determine the output signal.
•
Output - Signal provided by the ECU that controls operation of the load.
Symptoms ECU-controlled load circuits can have these malfunction symptoms: •
The load does not operate or ...
•
The load operates all the time, or ...
•
The load operates at the wrong time
These symptoms can be caused by missing or incorrect sensor input signals, the logic inside the ECU, or the output circuit. Troubleshooting Tip #15: Correct output signals from electronically-controlled circuits require correct input signals.
86
ELECTRONICALLY CONTROLLED CIRCUITS
ECU Inputs Input sensors for electronically controlled circuits report information to the ECU. The ECU uses input information to determine how to control output loads. There are two types of ECU inputs: •
Digital signals
•
Analog signals
Digital signals are ON-OFF voltage pulses, typically 2.5 or 5 volts. An example of a digital input device is the camshaft position sensor which creates a camshaft position signal. A typical digital signal looks like this:
Analog signals are produced by sensors that mechanically change resistance to deliver variable voltage signals within a fixed operating range. These components are called variable resistors or potentiometers. On vehicles, analog signals can come from: •
Throttle position sensor
•
Fuel tank gauge units
•
Vehicle speed sensor
A typical analog signal looks like this:
While potentiometers change resistance mechanically, electronic components also provide variable analog inputs to ECUs. These electronic, variable resistors are called thermistors or thermal transmitters (see page 29). Thermistors change their internal resistance based on temperature changes. Examples of thermistors include: •
Engine coolant temperature sensors
•
Intake air temperature sensors
•
EGR temperature sensor
•
Fuel tank temperature sensor
•
Ambient temperature sensor Thermistor
ELECTRONICALLY CONTROLLED CIRCUITS
87
Electronic Control Units (ECUs) The ECU in a circuit compares the input voltage it receives with data stored in its memory. This type of analysis by the ECU results in an output from the ECU. As we said, ECU system outputs rely on the inputs for the system to operate correctly. Note Note: Correct output from electronically controlled circuits requires correct input. To process voltage inputs and to produce outputs, ECUs have two operating memories: Read Only Memory (ROM) and Random Access Memory (RAM). ROM and RAM work together to evaluate inputs and deliver the appropriate output signal. ROM is permanently programmed with the operating data necessary to control output. For example, ROM in a timer control unit stores data to control the length of time the interior lights stay on after the doors have closed. The ROM program is “burned” into the electronic chip in the ECU and is not dependent on a power supply to maintain program data. Since one input sensor can affect several outputs, the ROM program is very complex. ROM can take into account all the various combinations of inputs to make the correct output decisions. Unlike permanently programmed ROM, RAM can create and store new data in addition to reading previously stored information. An example of RAM is the ECU built into a digital car radio for the station selection memory switches. Because RAM is dynamic, it requires an uninterrupted power supply to maintain its stored values. If battery power is disconnected from the radio or if the battery goes dead, all RAM is lost and the station selections must be reprogrammed. Note Note: When servicing a vehicle with an electronic radio, write down the radio station presets before you disconnect the battery.
88
ELECTRONICALLY CONTROLLED CIRCUITS
ECU Outputs There are three types of outputs from electronically-controlled circuits: •
Reference (typically 5 volts) constantly ON or OFF
•
Ground constantly ON or OFF
•
Pulsed reference or ground
Switched ECU voltage or ground can be measured using a voltmeter or oscilloscope. Voltmeter readings of pulse only indicate the average voltage present. On the other hand, an oscilloscope displays exact voltages as shown in the illustration at right. To diagnose the operation of ECU circuits, measurements must also include: •
Frequency (Hz)
•
Duty cycle (% ON)
•
Pulse width (Duration ON)
Cycle A complete cycle occurs when voltage is pulsed high, then low, then high again. It is said to be measured from start-to-finish (digital) or peak-to-peak (analog). See the following illustrations.
Cycle
(Digital Signal) (Analog Signal)
Frequency
Cycle
A pulse occurs when current is switched ON, then OFF. Each pulse or cycle starts when the current switches ON and ends when it switches ON again. The frequency of the pulse is determined by how often the current cycles ON and OFF per second. The unit of measurement for frequency is Hertz, often abbreviated Hz. Frequency merely expresses the number of cycles per second (cps) the pulsing occurs.
OFF
Voltage high (circuit OFF)
ON
Voltage “pulled low” (circuit ON) (Ground switched ON)
ELECTRONICALLY CONTROLLED CIRCUITS
89
The operation of a flywheel sensor is an example of how frequency is used to meet the operating requirements of an engine. As engine speed changes, the frequency of the sensor input changes. The ECM uses this sensor input to monitor engine misfire. A vehicle speed sensor is a good example of how frequency is used as an input to the ECM. Rotating Magnet Speed Sensor
Dashboard Control Unit
ECM
Signal at 15 mph Rotating Magnet Speed Sensor
Dashboard Control Unit
ECM
Signal at 40 mph Duty Cycle % Frequency alone however, is not sufficient to describe pulsed signals. In some cases frequency remains constant, but the length of ON time changes. Duty cycle is measured as percentage. For example, a duty cycle of 50% means that the % of ON time and OFF time is the same. If the ON time is 25% of the cycle, the duty cycle is 25%. 1Hz 50% Duty 5V 0V
Voltage high, output device OFF
1Hz 25% Duty
Voltage low low,, output device ON
Éxamples: •
Idle control solenoids
•
Shift solenoids A & B found on electronically-controlled automatic transmissions
•
Lock-up torque converter solenoids
•
Automatic transmission line pressure solenoids
90
ELECTRONICALLY CONTROLLED CIRCUITS
5V 0V
Measuring Duty Cycle Electronic test equipment reads and measures the duty cycle and displays an average that is the result of readings over a long period of time. Duty cycles are used to control actuators such as the auxiliary air control (AAC) valve of the ECCS system. The position of the AAC valve controls engine idle speed and is determined by the average amount of ON time in relation to OFF time. Pulse Duration (Time ON) Pulse duration is similar to duty cycle. However, while duty cycle is a percentage of ON time in relation to OFF time of the signal, pulse duration is more accurate. Rather than take an average reading over a long period of time, pulse duration is a measurement of the length of time the signal is ON, usually in milliseconds (thousandths of a second). Changes in pulse duration affect the operation of some components. When the ECCS control unit determines the engine requires more fuel, fuel injector pulse duration increases allowing the injector to stay open longer. The ECM makes constant adjustment to fuel injector ON-time meeting the engine's everchanging fuel volume needs based on input from the camshaft position sensor (rpm). Or, simply stated, the ECM changes pulse duration (injector ON-time) by increasing or decreasing the amount of fuel delivered to the combustion chamber. To review: •
Frequency is the number of cycles per second.
•
Duty cycle is the percent (%) of time an output is ON in a cycle.
•
Pulse width is the length of time a signal is ON, usually measured in milliseconds (msec).
For electronically controlled circuits to operate, inputs from sensors are processed by the ECU and outputs sent to actuator circuits. The ECU is the processing center for these signals. However, if an ECU output load is inoperative always check the ECU inputs. As with all computer controlled circuits, the acronym GIGO is important to remember: Garbage In, Garbage out.
ELECTRONICALLY CONTROLLED CIRCUITS
91
Depending on the type of signal, ECU inputs and outputs can be measured using: •
A Duty Cycle Meter
•
A Pulse Duration Meter
•
An Oscilloscope
•
A Multimeter
•
A Logic Probe
•
CONSULT (Nissan/Infiniti Scan Tool)
When checking an output load in an ECU controlled circuit, supply the missing link to verify output circuit operation. Remember the circuit requirements of source, load and ground. During diagnosis, be careful because the loads in some ECU-controlled circuits use dropping resistors. Never bypass one of these resistors to operate such circuits or wiring could overheat due to higher current flow. Fill in the blanks with the correct answer: •
A __________is an event that includes voltages changes from start-to-start, or peak-topeak.
•
The number of times a cycle repeats in a second is measured in ___________.
•
The percentage of ON time during a cycle is expressed as ____________.
•
The length of time a pulsed signal is ON during a cycle is referred to as __________________.
•
An example of a frequency input is _______________________.
•
An example of a duty cycle output circuit is ____________________.
•
An example of a pulse duration output circuit is __________________.
Troubleshooting Tip #16: Electronically-Controlled Units: When servicing a vehicle with an electronic radio, write down the radio stations before you disconnect the battery.
92
ELECTRONICALLY CONTROLLED CIRCUITS
ELECTRICAL DIAGNOSIS Diagnosing electrical malfunctions, like any other vehicle system, involves investigating the cause of the problem and reaching a conclusion based on your investigation. Accurate diagnosis requires understanding how the specific system functions, then evaluating whether it functions as designed. Basic diagnosis involves the following steps: 1.
Verify the complaint .............
Apply knowledge and use reference materials to find possible causes
2.
Isolate ..................................
Inspect and/or test for the possible cause in a logical order
3.
Repair ..................................
Diagnosis conclusion
4.
Recheck ..............................
Make sure the customer complaint is corrected
Inspect and diagnose, then notify customer.
Fuel tank gauge doesn’t work
Neal Barnes
ELECTRICAL DIAGNOSIS
93
Preliminary Diagnosis Tips: Step 1: For unfamiliar circuits, start with the schematic diagram. This provides an overview of the circuit. The schematic diagram shows circuit components and how they are connected. Always locate the circuit load first, then trace the wires back to the battery and ground, if necessary. Check fuses and fusible links protecting the circuit in question. Step 2: Use the wiring diagram for a complete picture of the circuit. The wiring diagram is the best source to logically trace the circuit. It includes information such as wire colors, connector numbers and relay box layout. Use your knowledge of source, load and ground along with the wiring diagram to help isolate the circuit for testing. Step 3: The Harness Layout section of the service manual describes specific harness and connector locations on the vehicle. The harness layout diagram will help you find the exact locations on the vehicle to perform your diagnosis. Step 4: Finally, locate the actual components and the most accessible test points by using the Location of Electrical Units section of the service manual.
On-Car Troubleshooting Tips: •
Always check the source voltage (at the battery) before testing circuit voltage.
•
Visually inspect the battery connections for looseness or corrosion.
•
Clean and tighten battery cables as necessary.
•
Check available voltage at the load and compare it to the source voltage. If it is not the same or nearly the same, there is an abnormal voltage drop between the battery and the load. Look for poor connections, frayed wires, etc.
•
Check tightness and the condition of ground connections.
•
Simulate the conditions of the problem.
94
ELECTRICAL DIAGNOSIS
Diagnosing Malfunctions in Circuits with Fuses or Fusible Links Isolate malfunctions in circuits protected by fuses or fusible links by following these steps: •
Locate the wiring diagram for the circuit that has the failed (melted) fuse or fusible link.
•
Make a note of all loads that operate on that circuit. There may be multiple loads protected by a single fuse or fusible link.
•
Disconnect the circuit loads one at a time to isolate which circuit load is causing the fuse to fail. You may have to install a new fuse to check each individual circuit. For more efficient testing, temporarily replace the fuse or fusible link with a circuit breaker that will reset by itself.
•
If the fuse or fusible link still fails after all circuit loads are disconnected, you may have to separate the harness to locate the malfunction.
Note Note: Always check for pinched wires in areas where work has recently been performed resulting from body repairs. When diagnosing faults in circuits that use fuses and fusible links: •
Verify the contact between the fuse and fuse holder is clean and tight. Poor contact increases circuit resistance. The excessive heat caused by the poor connection may eventually cause the fuse to melt.
•
Always use a fuse with the proper rating. If a fuse with a higher rating is used, the fuse will not fail (melt) as designed. This could result in burned wiring or insulation.
•
A bad fuse or fusible link cannot always be detected from the outside. Always use reliable test equipment to check for open circuits.
•
Be careful when removing a bad fusible link. When a fusible link melts, it becomes very hot. This heat can burn you or damage nearby wiring.
ELECTRICAL DIAGNOSIS
95
Connector T erminal Malfunctions Terminal
Vibration T ests Tests
Tap gently
Shake gently Bend gently
Connecting a meter to a connector terminal can damage it if the tester probe enlarges the opening. Use a T-pin designed for meter connections. Probe it from the wire harness side of the connector. Inspect terminals for damage from previous probing. Note Note: T-pins are available in different sizes at local hobby stores.
96
Connector
Alligator clip “T” pin
DMM
ELECTRICAL DIAGNOSIS
Available Voltage and Voltage Drop Tests The following illustrations describe two methods of diagnosing a circuit using a voltmeter. Use the available voltage method to determine if source voltage is available to the load. Measuring Available V oltage Voltage
1.
Connect the voltmeter across the connector or part of the circuit you want to check. The voltmeter + lead should be closer to the battery and the – lead closer to ground.
2.
Operate the circuit.
3.
The voltmeter will indicate how many volts are availalbe in that part of the circuit.
In this circuit, the available voltage to the load is only 7.9 volts due to excessive resistance.
Use voltage drop tests to find components or circuit branches which have excessive resistance. Measure V oltage Drop – Step by Step Voltage 0V (OK)
0.1V (OK)
7.9V (dim bulb)
V
V
V
0V (OK) V
Switch 4V V Battery
12V V
Excessive Vdrop
Connection with high resistance
1. Connect the voltmeter as shown, starting at the battery, then work along the circuit. 2. An unusually large voltage drop indicates a component or wire needs repair. The poor connection in the illustration shows a 4 volt drop. In this circuit, excessive circuit resistance has dropped the available voltage by 4 volts.
Note Note: Each connection can (potentially) be the source of an “unwanted” or excessive voltage drop. Normal voltage drop at each connection should be 0.1 volt or less.
ELECTRICAL DIAGNOSIS
97
Testing for Opens in a Circuit Before diagnosing a system, draw a rough sketch of the system. This helps simplify the system and reinforces your working knowledge of the system. Diagnose for Open Circuit:
Ignition OFF when testing resistance (Ω). Ignition ON for voltage testing.
Available Voltage and Continuity Tests Another method to pinpoint the cause of a circuit malfunction is to first use the voltmeter to measure available voltage throughout the circuit. When no voltage is found where there should be voltage, switch the source OFF and open switches to isolate the suspected circuit. Use the multimeter in the ohmmeter mode to measure the continuity between test points. The above illustration shows two opens at A and B. Note how the ohmmeter is connected to each part of the suspected circuit to isolate the area causing the open circuit.
98
ELECTRICAL DIAGNOSIS
Testing for Shorts in a Circuit Diagnose for Short Circuit
Resistance Check Method 1.
Disconnect the battery negative cable and remove the blown fuse.
2.
Disconnect all loads powered through the fuse (SW1 open, relay disconnected and solenoid disconnected).
3.
Connect one ohmmeter probe onto the load side of the fuse terminal. Connect the other probe to a known good ground.
4.
With SW1 open, check for continuity (complete circuit). Continuity: The short is between the fuse terminal and SW1 (Point A) No Continuity: The short is further down the circuit (after SW1)
5.
Close SW1 and disconnect the relay. Connect the ohmmeter probes on the load side of the fuse terminal and a known good ground, then check for continuity. Continuity: The short is between SW1 and the relay (Point B) No Continuity: The short is further down the circuit (after the relay)
6.
Close SW1, then connect a jumper wire onto the relay contacts. Connect probes at the load side of the fuse terminal and a known good ground, then check for continuity. Continuity: The short is between the relay and the solenoid (Point C) No Continuity: Check the solenoid, then retrace your steps
Voltage Check Method 1.
Remove the blown fuse and disconnect all loads (Open SW1, disconnect relay and solenoid) powered through the fuse.
2.
Turn the ignition switch to the ON or START position. Verify battery voltage at the B+ side of the fuse terminal (DMM leads to B+ terminal of fuse block and known good ground).
3.
With SW1 open, check for voltage. Voltage: The short is between the fuse block and SW1 (Point A) No Voltage: The short is further down the circuit (after SW1)
4.
With SW1 closed, relay disconnected and the DMM leads across both fuse terminals, check for voltage. Voltage: The short is between SW1 and the relay (Point B) No Voltage: The short is further down the circuit (after the relay)
5.
With SW1 closed, jump the relay with a test lead, solenoid disconnected, then check for voltage. Voltage: The short is down the circuit of the relay or between the relay and the disconnected solenoid (Point C). No Voltage: Retrace steps and check power to the fuse block.
ELECTRICAL DIAGNOSIS
99
Ground Inspection Ground connections are very important for the proper operation of electrical and electronic controls. Ground connections are often exposed to moisture, dirt and other corrosive elements. This corrosion (rust) can become an unwanted circuit resistance and prevent the circuit from operating properly or at all. Loose connections also create excessive circuit resistance. Ground Inspection
Remove bolt (screw)
Inspect mating surfaces for tarnish, dirt, rust, etc. Clean as required to assure good contact
Diagnostic Tips for Relays When diagnosing faults on relay-controlled circuits: •
Listen to or feel the relay click
•
If no click is heard or felt, remove the relay and connect a fused jumper as shown in the illustration at right: - If the load now works,you have learned that the load and ground are good. - If the load does not work and system voltage is available to the relay, look for circuit malfunctions on the load side of the relay circuit.
Note Note: Never jump the terminals for the coil control circuit (pins #1 and #2) because higher than normal current can damage the wiring of the control circuit. Jumping across these terminals will blow the fuse for this circuit or even damage the ECU that controls the circuit.
100
ELECTRICAL DIAGNOSIS
Color (Appl)
Relay T ype Type
Relay Symbols
One Make Relay (1M) Control circuit terminal nos. Blue or Yellow
#______ and #______
(All Models)
Contact circuit terminal nos. #______ and #______ One Make Relay (1M) Control circuit terminal nos. Blue or Green
#______ and #______
(‘95 & older)
Contact circuit terminal nos. #______ and #______ One Make Relay (1M) Control circuit terminal nos. #______ and #______
Blue, Gray, or Yellow (All Models)
Contact circuit terminal nos. #______ and #______ Two Make Relay (2M) Control circuit terminal nos. #______ and #______
Brown (All Models)
Contact circuit terminal nos. #______ and #______ #______ and #______
ELECTRICAL DIAGNOSIS
101
Relay T ype Type
Color (Appl)
Relay Symbols
One Transfer Relay (1T) Control circuit terminal nos. #______ and #______ Contact circuit terminal nos. Not energized: #___ & #___ Energized:
Black (‘95 & newer, some circuits)
#___ & #___
One Transfer Relay (1T) Control circuit terminal nos. #______ and #______ Contact circuit terminal nos. Not energized:
#___ & #___
Energized:
#___ & #___
Black (‘95 & older)
One Make-One Break Relay (1M-1B) Control circuit terminal nos. #______ and #______
Gray (All models)
Contact circuit terminal nos. Not energized:
#___ & #___
Energized:
#___ & #___
Note Note: A relay removed from a circuit can be tested in the following manner: 1. 2. 3. 4.
102
Connect voltage to terminal #1. Connect terminal #2 to a good ground. Listen for a click. Use a multimeter to check continuity between the output terminals. If there is continuity, the relay is working. If not, replace the relay.
ELECTRICAL DIAGNOSIS
Diagnosis (Electronic Control Units) In the following illustration, the ECU is programmed to light the bulb when switch “A” and switch “B” are ON and switch “C” is OFF. To diagnose a symptom of non-operation, separate the input and output sides of the circuits. Begin by checking the output at the ECU wire connector. Remember, ECU-controlled outputs have the same requirements for source, load, and ground as any relay-controlled circuit. If an output signal is present, disconnect the ECU wire connector and check the operation of the load with a jumper wire. Depending on how the load is wired, apply either voltage or ground for the load to operate.
If the load operates when source or ground is applied, go to the input side of the ECU circuit. With the wire connector removed from the ECU, check the inputs at the ECU wire connector to be sure they are good. As in the example shown, some ECU output loads require more than one input to operate. If the inputs are good and there is no output to the load, the ECU is defective. Diagnosis (Thermistor circuits) To diagnose circuits containing thermistors, check the resistance of the thermistor and compare that to specifications. Then check circuit continuity between the ECM and the load (thermistor).
ELECTRICAL DIAGNOSIS
103
Motors Symptoms •
Motors are controlled by a switch, a relay or an ECU (Electronic Control Unit). If an electrical failure occurs, it could be caused by an open circuit, preventing the motor from operating. A short circuit inside the motor or within the circuit will cause the fuse or fusible link to fail.
•
Motors can also fail mechanically. A mechanical failure will also cause the motor to be inoperative. If the motor armature binds (stops rotating), electrical resistance decreases and amperage increases which causes the fuse to fail.
Diagnosis •
If a motor circuit does not operate, check the fuse or fusible link for the motor circuit. For motor circuits that are relay controlled, use the same procedures to isolate the malfunction as explained previously for other relay-controlled loads.
•
Motors that must rotate in both directions are switch-controlled. For example, if a window motor is “stuck” in the down position there could be an open circuit in the “up” contacts of the switch. To quickly check a window motor circuit, switch the ignition ON and watch the vehicle interior lights. If the lights dim slightly when you press the window switch to the “down” position, there is a complete circuit through the motor “down” circuit. If the lights do not dim when pressing the switch to the “up” position, the switch could be bad. If the lights dim when the switch is pressed to the “up” position, the motor could be mechanically stuck.
•
If the fuse or fusible link is bad, use the isolation procedures for fused circuits to determine whether the malfunction is electrical. If you suspect a mechanical failure, remove the motor from its operating position and bench test it by applying power and ground. Be sure to use test wires with an in-line fuse. If the motor operates on the bench, check the linkage or mechanical components that the motor drives to be sure they are not binding. Check wire routing during the inspection. Wires can sometimes get tangled in the linkage and ground the motor circuit.
104
ELECTRICAL DIAGNOSIS
Meter and Gauge Diagnosis Symptom: The speedometer reads inaccurately (too fast or too slow) •
Speed sensor malfunction. Check wiring harness continuity and check speed sensor signal according to service manual procedures and specifications. Check condition of speed sensor signal using CONSULT data monitor function.
•
Vehicle may have oversize tires. - Oversize tires reduce axle speed which reduces speedometer reading. - If oversized tires are installed on the vehicle, no corrections should be made other than to recommend correct tire application.
•
A problem with a speed sensor may also appear at the engine ECM as well as the A/T and ASCD control units. - The revolution sensor is the primary input. The speed sensor will tell the A/T control unit when to shift if the revolution sensor circuit fails. If the speed sensor or revolution sensor circuit fails, the transmission O.D. light should blink for 7 seconds after every vehicle start indicating a code is stored in the A/T control unit. Don’t forget to verify proper cruise cable adjustments. - A/T control unit: Speed sensor input is used as a backup for the revolution sensor input. Transmission may not indicate a symptom caused by a bad speed sensor. - ASCD control unit: Speed may not set correctly if the control unit gets an inaccurate or erratic speed input. Check wiring harness continuity and speed sensor signal according to service manual specifications.
Symptom: Indicators do not operate •
Check battery voltage input to the combination meter/microcomputer. - If voltage is not present, trace and diagnose the circuit back to the power source. - If the fuse is blown, look for a short between the fuse and the speedometer.
Symptom: Fuel gauge has inaccurate indication •
Check fuel tank gauge unit adjustment according to service manual specifications. - Check wiring harness continuity between the gauge unit and speedometer. - If resistance is out of specification the gauge will register lower than normal fuel level.
•
Check Nissan’s ASIST® system for additional possibilities.
•
Inspect hose and pipe connections in tank for mechanical interference.
ELECTRICAL DIAGNOSIS
105
Note Note: Quest only • If resistance is higher than the specification, the gauge reading will be higher than the actual fuel level; if resistance is lower than the specification, the gauge reading will be lower than the actual fuel level. All other Nissan models: • If resistance is higher than the specification, the fuel gauge reading will be lower than the actual fuel level; if resistance is lower than the specification, the gauge reading wil be higher than the actual fuel level.
106
ELECTRICAL DIAGNOSIS
Meter and Gauge Checks Thermal Transmitter Check To verify the thermal transmitter is operating properly, check the resistance between the terminals of the thermal transmitter and body ground. The thermal transmitter is a variable resistor that affects the temperature gauge by controlling current (amperage) in the circuit.
Water T emperature Temperature
Resistance
60°C (140°F)
Approx. 70-90 ý
100°C (212°F)
Approx. 21-24 ý
Fuel Tank Gauge Unit Check To verify the unit operates properly, check the resistance between terminals 3 and 2 (see the following diagram). (Note: To remove the fuel tank gauge unit refer to the FE section in the service manual.) The fuel tank gauge unit is a variable resistor that affects the fuel gauge reading by controlling current (amperage) in the circuit. Note Note: The illustration that follows is an example of a test and specification chart for a fuel tank gauge unit. Tank gauge units for each vehicle are not the same. The resistance varies with each one, so be certain you refer to the service manual when performing this procedure.
Ohmmeter connection
+
3
Float Position, mm (in.)
–
2
Resistance Value (ý)
*1
Full
95 (3.74)
Approx. 4-6
*2
1/2
184 (7.24)
31-34
*3
Empty
265 (10.43)
80-83
*1 and *3: When float rod is in contact with stopper
ELECTRICAL DIAGNOSIS
1999 Pathfinder
107
Nissan Original Equipment Battery Ratings Note: For original equipment batteries, the label showing the rating is located on the top of the battery
Model Xterra
Year 2000 & later 2000 & later 1997-98 1999 & later 1997 1998 & later 1997 & later 1997-99 1999.5 1997-98 1997-98 1997 & later 1997 & later 1997-98 2000 & later 1997-99 1997-99
Quest Truck Frontier Pathfinder 200SX Sentra Altima 240SX Maxima
Application Standard Optional All All All All Standard Optional Optional Standard Optional All All All All Standard Optional
Rating 490 CCA 550 CCA 550 CCA 525 CCA 490 CCA 490 CCA 55D23R 75D31R 80D26R 490 CCA 550 CCA 490 CCA 550 CCA 55D23R 80D26L 55D23L 80D26L
Genuine Nissan Replacement Battery Ratings Note: For original equipment batteries, the label showing the group rating (i.e., 24, 25, 27, etc.) is located on the top of the battery
Model Altima Axxess Maxima Pulsar Stanza
Sentra Pathfinder Frontier
Truck Quest Van 200SX
240SX
300ZX Xterra
Year 1993 & later 1990 1985 & later 1985 & later 1984 1984-90 1987-92 1984-86 1986-88 1987- & later 1985-86 1984 1987 & later 1987 & later 1999 & later 1999 & later 1984-97 1986 1982-85 1993 & later 1987-90 1995 & later 1982-88 1995-98 1989-94 1992-94 1990-96 1992-96 1984-89 2000 & later 2000 & later
Application All All All With cold package24F All All All All except Wagon Wagon All All except diesel All except diesel All All with heated seats Four cylinder Six cylinder All except diesel Diesel Diesel All All All All All All exc. convertible 24 Convertible All Convertible All All (standard) All (optional)
Group # 24F 35 35 25 35 35 25 35 35 24F 35 25 24 25 24 25 24 (2) 27 24F 25 25 24 25 25 24F 35 25 25 24
Nissan P/N 999M1-NB24F 999M1-NB35C 999M1-NB35C 999M1-NB24F 999M1-NB25C 999M1-NB35C 999M1-NB35C 999M1-NB25C 999M1-NB35C 999M1-NB35C 999M1-NB24F 999M1-NB35C 999M1-NB25C 999M1-NB24C 999M1-NB25C 999M1-NB24C 999M1-NB25C 999M1-NB24C 999M1-NB27C 999M1-NB24F 999M1-NB25C 999M1-NB35C 999M1-NB24C 999M1-NB25C 999M1-NB24C 999M1-NB25C 999M1-NB24F 999M1-NB35C 999M1-NB25C 999M1-NB25C 999M1-NB24C
CCA* 575 525 525 575 525 525 525 525 525 525 575 525 525 575 525 575 525 575 660 575 525 525 575 525 575 525 575 525 525 525 575
*CCA = Cold Cranking Amps
108
ELECTRICAL DIAGNOSIS
GLOSSARY OF TERMS Alternating Current (AC) - Current that reverses its direction at regular intervals. Amperes (amps) - Unit of measure for current flow in an electrical circuit. Ammeter - An electrical test meter that measures the amount of current flow, in amperes, in a circuit. Analog multimeter - A device that measures voltage, resistance and current. The numerical measurement is represented by a dial-type needle that points to the numerical value on one of many scale ranges. Battery - A device consisting of two or more cells for converting chemical energy into electrical energy. Coil - Thin wire wound into a circular shape, usually around an iron core. Current passing through the coil creates a strong magnetic field to assist in electrical contacts and other circuit functions. Circuit - An assembly consisting of a voltage source, a load, a control device (such as a switch and a ground path. A circuit carries electricity through a load to produce some type of work, such as heat, light or motion. Circuit breaker - A mechanism designed to break or open the circuit when certain conditions exist; usually heat sensitive. Circuit protection - A device which is used to protect wiring and electrical devices from excessive current flow, so that they are not damaged. Combination Circuit - A circuit which combines series and parallel circuits. Conductor - The device which connects electrical components together so current can flow in a circuit. Electrical conductors are more commonly referred to as wires. The most common conductors are copper and aluminum, but gold is also a good conductor. The metal vehicle chassis is also a conductor. Connector - A mechanical device to connect single or multiple terminals. Usually surrounded by an insulating material to electrically separate the conducting material. Continuity - A complete path for current flow. In the service manual, continuity does NOT necessarily mean “0” ohms resistance. Conventional current flow theory - The theory that states that current flows from the positive post of the battery through the external source side of the circuit, through the circuit loads and back to the battery via the ground circuit.
GLOSSARY OF TERMS
109
Crossed Circuit - A malfunction. Current flow from a switch operates a LOAD from a different, unrelated circuit. Current Flow - The movement of electrons in a circuit. Also called amperage or electricity. Digital Multimeter - A device that measures voltage, resistance and current. The numerical measurement is shown in numbers using a LCD or LED display. Also called a digital voltohmmeter. Diode - An electrical device that acts like one-way check valve. It permits current flow in one direction, but stops it from flowing in the other direction. Direct Current (DC) - Current that flows in one direction only. ECU - Electronic Control Unit. An electronic logic device to operate electronically-controlled circuits. Electromagnet - A temporary magnet constructed by winding a number of turns of insulated wire into a coil or around an iron core. It is energized by the flow of current through the coil. Used in relays and solenoids. Fuse - A type of circuit protection device that has a thin metal segment that melts when its rated current-carrying capacity is exceeded. When this occurs, the circuit can not be completed until the faulty fuse is replaced. Fuse block/junction block - A grouping of fuses. A connection point for circuit wires to separate to other circuits. Fusible link - A type of circuit fuse that uses a length of heat sensitive conducting wire to protect a circuit. Grounded Circuit - A circuit in which there is an unwanted contact between a conductor and ground. On the SOURCE side of a circuit, this will cause the fuse to blow. On the ground side of the circuit, the LOAD may be ON all the time. Group # (battery) - The storage battery size to mount into a specific vehicle. Insulator - A material that will not allow current flow. Also, the material that separates conductors, providing a barrier that shields them from interfering with each other. Insulators are more commonly referred to as the wrapping, or sheaths around wires. The most common insulating materials are plastic and rubber because they have excellent insulating properties yet remain very flexible. Light emitting diode (LED) - A type of diode that emit light when current flows from anode to cathode. They normally emit red light, but other colors are available, including INFRA-RED LEDs. They conduct current in one direction only, but can be damaged by reverse voltages.
110
GLOSSARY OF TERMS
Magnetic field - The property exhibited by certain substances and produced by electron (or electric current) motion which results in the attraction of iron. Motor - A device for converting electrical energy into mechanical energy. Multimeter - A device that measures voltage, resistance and current (see analog and/or digital multimeter). Ohms - Unit of measure for resistance of electrical devices or circuits. Ohm’s Law - A basic statement of the relationship between volts, amps and ohms. Ohmmeter - A device for measuring ohms resistance of a circuit or electrical device. Open Circuit - An incomplete circuit in which current cannot flow from SOURCE to LOAD to GROUND because of a disconnection, broken wire, blown fuse or other interruption. Parallel circuit - A circuit in which there is a separate path for current flow for each LOAD. If one of the LOADs has an open circuit, the other loads will continue to operate. Potentiometer - A variable resistor that is mechanically operated. Parasitic load (draw) - Electrical current from the battery that exists when the vehicle is not operating. Polarity - A term relating to the direction of current flow in a circuit. For instance, a circuit is said to have positive polarity when the current flows from positive to negative. Primary ignition (primary circuit) - Equivalent to SOURCE voltage; the circuit used to signal or switch the ignition system. Rectifier (rectify) - An electrical device that changes alternating current to direct current. Relay - An electrically-operated switch that uses low current flow in the coil control circuit to activate higher current flow in the contact point circuit. Reserve capacity - The ability of a battery to sustain current output when connected to a circuit or a specified test load. Storage batteries are usually rated in Cold Cranking Amperes (CCA). Resistance - The opposition or reluctance to current flow in a circuit. Resistance is expressed in ohms, represented by the symbol Ω (omega). Secondary ignition (secondary circuit) - The circuit that creates a high voltage spark; operates with and controlled by the primary circuit. Semi-conductor - A device that is neither an insulator nor a conductor. With certain materials added to their makeup, semi-conducting devices can be made into conductors. Semiconductors are more commonly known as transistors, diodes and electronic control devices. GLOSSARY OF TERMS
111
Series circuit - A circuit in which there is only a single path for current flow. If one of the components or LOADS in the circuit becomes open, the circuit no longer operates. Series-parallel circuit - The electrical circuit formed when series-connected circuit elements are combined with parallel-connected circuit elements. Shorted Circuit - A circuit in which current flow takes a shorter path (less resistance) between SOURCE and GROUND, bypassing part or all of the circuit LOAD. Short circuits increase current flow and can cause blown fuses. Solenoid - A device that allows electricity to pass through a coil of wire to create magnetism. A mechanical lever moves as a result of the electromagnetism. Source - A supply of voltage to operate a circuit. Specific gravity - The ratio of the weight of a substance to the weight of an equal volume of chemically pure water at 39.2°F; used to measure the state of charge of a lead-acid storage battery. Static electricity - Accumulated electrical charges, usually considered to be those produced by friction. Storage Battery - A lead-acid electrochemical device that changes chemical energy into electric energy. The action is reversible; electrical energy applied to the battery stores chemical energy. Sulfation - A term used to describe a chemical condition that occurs within a battery when the electrolyte has degraded to a condition that does not produce normal voltage. When a battery is heavily sulfated, the electrolyte and plate material combine into a hardened substance (the sulfate) which settles to the bottom of a cell, causing the cell to not accept a charge or deliver current. When this occurs, the battery is not serviceable because this condition is irreversible. Terminal - The metal connector attached to the end of a length of stranded wire which is used to connect to another component or wire. Thermistor - An electronic component that changes its resistance as its temperature changes. Transistor - A semiconductor switching device. Can be used as a switch or a relay. Variable Resistor - A component whose resistance value can be changed to change to operation of a LOAD in a circuit. Volt - A unit of measure of electrical pressure (voltage). Voltage (electrical potential) - The electrical pressure required to push a current of electricity through a circuit. Voltage is chemically produced in a lead-acid battery or from an electromagnetic field, such as in an alternator.
112
GLOSSARY OF TERMS
Voltage drop(s) - The amount of voltage consumed by a LOAD during circuit operation. The total of all voltage drops in a circuit is equal to the available voltage. A concept which describes what occurs in a circuit when current passes through a load. A load in this case is loosely defined as anything that causes resistance. This can include corrosion or looseness in wiring and connections, fixed or variable resistance, or devices such as bulbs or motors. Voltmeter - An electrical test meter that measures the amount of voltage or electrical pressure in a circuit. Wiring/ wire gauge - Diameter of a wire. Smaller gauge wire (larger number) can carry less current. Zener diode - A semiconductor. This type of diode conducts electricity in the reverse direction from normal diodes. To pass electricity through a zener diode, it must be around eight to ten times the value of the normal diode, typically 4.7volts. When four diodes are connected in a certain way (i.e., "bridged") they will convert AC to DC, as in an alternator.
GLOSSARY OF TERMS
113
NOTES
114
NOTES
M O D U L E S
Date of Class
ELECTRICAL COMPONENT DIAGNOSIS AND REPAIR SIGN-OFF SHEET WORKSHEET
TITLE
Module 1
Locate Service Manual Information
Module 2
Interpret Service Manual Information
Module 3
Measuring Available Voltage
Module 4
Measuring Voltage Drop
Module 5
Measuring Resistance
Module 6
Measuring Current
Module 7
Combination Switch Operation
Module 8
Diagnosing One Transfer (1T) Relay Malfunctions
Module 9
Diagnosing One Make (1M) Relay Malfunctions
Module 10
Diagnosing Two Make (2M) Relay Malfunctions
Module 11
Diagnosing One Make-One Break (1M-1B) Relay Malfunctions
Module 12
Circuit Diagnosis Exercise #1
Module 13
Circuit Diagnosis Exercise #2
Module 14
Circuit Diagnosis Exercise #3
Module 15
Circuit Diagnosis Exercise #4
Module 16
Circuit Diagnosis Exercise #5
Module 17
Circuit Diagnosis Exercise #6
Module 18
How to Use a Digital Multimeter
Module 19
Fuel Guage Unit Testing
Module 20
Service Manual Electrical Symbols
Module 21
Testing Batteries, Starters & Charging Systems
INSTRUCTOR
i
ii How to Use a Digital Multimeter Module 18
Measuring Available Voltage Module 3
Locate Service Manual Information Module 1
Measuring Current Module 6
Service Manual Electrical Symbols Module 20
Measuring Resistance Module 5
Interpret Service Manual Information Module 2
Measuring Voltage Drop Module 4
ELECTRICAL COMPONENT DIAGNOSIS AND REPAIR COURSE MAP
Introduction Terminology Service Manual Meter Familiarization
Combination Switch Operation Module 7
Fuel Gauge Tank Unit Testing Module 19
Diagnosing One Transfer (1T) Relay Malfunctions Module 8
Circuit Diagnosis Exercise: #1 Module 12
Diagnosing One Make (1M) Relay Malfunctions Module 9
Circuit Diagnosis Exercise: #2 Module 13
Diagnosing Two Make (2M) Relay Malfunctions Module 10
Circuit Diagnosis Exercise: #3 Module 14
Diagnosing One MakeOne Break (1M-1B) Relay Malfunctions Module 11
Circuit Diagnosis Exercise: #4 Module 15
Circuit Diagnosis Exercise: #5 Module 16
Testing Batteries, Starters & Charging Systems Module 21
Circuit Diagnosis Exercise: #6 Module 17
iii
NOTES
iv
LOCA TE SERVICE MANUAL INFORMA TION LOCATE INFORMATION Module 1
Objective:
Given an Electronic Service Manual (ESM), locate wiring diagram descriptions and interpret the information.
Relevance: An important part of vehicle repair is the ability to locate diagnostic repair information. Both the General Information (GI GI)) and Electrical (EL) sections of the service manual contain useful information relating to circuit operation and testing. Resources: ASIST/ESM Skill Check: You will locate and identify electrical components, symbols and information in the ESM. You will identify navigation controls in the ESM.
Module 1
1
Use the ESM to answer the following questions: ECTC 0016C
1.
On what page in the GI section is the combination switch located? (See illustration on left). Page GI GI-_________________
2.
What page describes the connector symbol descriptions? Page GI GI- _________________
3.
In the illustration on the left, draw a circle around each symbol that identifies a male connector.
4.
Locate the pages that describe standardized relays in the service manual. What color is a 2M relay case? __________________________
5.
What pages in the EL section describe Power Supply routing? Pages EL EL-______ to EL EL-________
6.
Find the section that covers the location of Electrical Units. Other than relays, which other components are located in boxes under the hood? ____________________________________
2
Module 1
M Main
I Instrument
E Engine
S Sunroof
YSTEM wiring Locate the CHARGING S SY diagram in the service manual. What is the connector number for the Charge Warning Lamp?
F Eng. Control (EFI)
D Door
M__________________________________
A Alternator
B Body
T Tail
Z Air Bag
The chart on the left shows wiring harness code prefixes (“M” for main harness).
Harness Symbols
R Room (Interior Lamp)
7.
8.
Module 1
Find main harness connector locator information. What is the grid coordinate for the location of the charge warning lamp connector? __________________________________
9.
Using the illustration of the A/T control unit connector below as a reference, which side of the connector is in view? ____________________________________
Module 1
3
10. Some service manuals also show joint connector (J/C) locations. A joint connector shows that two or more wires are electrically joined together in a connector or a junction box.
ECTC 0016C
In the illustration below, which terminals are joined together in connector M1? ____________________________________
4
Module 1
11. Using the GI section as a reference, match the letter of each service procedure with the corresponding symbol in the spaces provided. a. b. c. d. e.
Disconnect Switch ignition to ON Harness side of connector Measure with an ohmmeter Do not start
12. Using the EL section as a reference, what type of relay has a gray case? ______________ Page EL EL-____ 13. Where is the ECM located? ____________________________________ 14. Locate the Power Supply Routing schematic in the EL section of the service manual. What amperage fuse protects the horn circuit? _____ Amp Page EL EL-____ What is the fuse number? _______________ a
b
15. What do the two symbols at left represent? a. _________________________________ b. _________________________________
Module 1
5
Module 1
16. Using the engine compartment Harness Layout page as a reference, which component connects to connector E15?
ECTC 0016C
___________________________________ 17. Find the engine control Harness Layout page. What is the connector number for the Throttle Position Switch? _______________
Page EL EL-_____
18. Identify the following navigation controls in the ESM by placing the cursor over the icon.
A
B
D
F
C ___ ___ ___ ___ ___ ___
6
E
Bookmark options Last views Search Commands Open navigation menu Print document or selected page(s) View first, previous, next or last page
Module 1
When using the ESM or ASIST, you have the ability to do keyword searches. Hold down the Ctrl key and select the letter “F” to begin the search. 19. Located in the lower left corner of the keyboard is the Ctrl key. Hold down the Ctrl key and then press the letter F . 20. Place the cursor in the box and type the word “Power”. Then select find find. You should have located the next place in this section with the word “Power”. You have just completed this worksheet. You should now be able to locate necessary information to read wiring diagrams. If you have any doubt about your skills in completing this worksheet, please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials ______________________ •
Module 1
Return the workstation to the condition that you found it.
7
Module 1
NOTES
8
Module
INTERPRETING SERVICE MANUAL INFORMA TION INFORMATION
Module 2
Objective:
Given an electronic service manual, interpret wiring diagram symbols and answer related questions.
Relevance: Your ability to diagnose electrical malfunctions depends on how well you can read and interpret vehicle wiring diagrams. Wiring diagrams illustrate how parts of an electrical circuit fit together. Wiring diagrams use electrical symbols to describe switches, connectors, motors, relays and fuses. There are also symbols for wire colors and where and how these wires connect to each other. Resources: ESM Skill Check: You will locate and identify electrical symbols and their descriptions in the GI section of an ESM.
Module 2
1
Use the GI section in the ESM to answer questions 1–16.
ECTC 0016C
1.
This illustration shows two halves of a connector. Circle the male side of the connector.
2.
The numbers in this connector represent terminal numbers. What is the terminal number for the ‘W’ wire? ___________________________________ What is the terminal number for the ‘B/W’ wire? ___________________________________
B=
BR=
L=
GY=
P=
PU=
LG=
SB=
G/B=
OR/B=
G/R=
Y/L=
3.
Locate the service manual page that describes the code for wire colors. Record the correct wire color next to the color code in the space provided in the chart.
4.
What do B1 and D0 represent in this illustration? (Check one) Connector location Super multiple junction terminal location Multiple switch terminal location
2
Module 2
5.
What do E5 and M4 indicate in the illustration? (Check one) Component location Connector number
Module 2
Terminal number
6.
What is the normal position of each of these switches? Switch A: __________________________ Switch B: __________________________
7.
Match the symbol on the left with the letter of its description below: A.
Do not start engine, or check with engine stopped.
B.
Circuit resistance should be measured with an ohmmeter.
C.
Check after disconnecting the connector to be measured.
D.
Turn ignition switch from “ON” to “OFF”.
E.
Voltage should be measured with a voltmeter.
F.
View from the harness side.
G.
Start engine, or check with engine running.
H.
Check after connecting the connector to be measured.
V
Module 2
3
8. ECTC 0016C
Examine the sample wiring diagram shown in the GI section. There are two types of wire splices: What do these symbols mean? a. _________________________________ b. _________________________________
9.
What type of meter is being used for the diagnosis shown at left? Ammeter / Ohmmeter / V oltmeter Voltmeter (Circle one)
10. What connector terminals must be tested? __________________________________ 11. On which side of the harness should you perform the inspection? Terminal / Harness (Circle one) 12. For the inspection shown at left, the harness connector should be: Connected / Disconnected (Circle one) 13. The engine should be: ON / OFF (Circle one) 14. What electrical test must be done? (Check one) Measure amperage Measure resistance Measure voltage
4
Module 2
15. Which connector terminal must be tested? ___________________________________ 16. Which side of the connector is the meter being probed? Terminal side / Harness side (Circle one) Refer to the charging system wiring diagram in the ESM for answers to questions 17–21. 17. What types of circuit protection devices are used in the charging system? ___________________________________ ___________________________________ 18. Both the fusible link and fuse shown at left have clear and dark circles. What do these circles mean? ___________________________________ Fusible link
Fuse
___________________________________ 19. How many pin openings are there in the charge warning lamp connector? ___________________________________ 20. What type of splice connects the battery to the charging circuit? ___________________________________ 21. Where is the alternator ground attached to the vehicle? (Check one) To a body ground under the dashboard To a body ground behind the right kick panel To a body ground in the engine compartment or to a chassis ground under the hood
Module 2
5
Module 2
Refer to the illustration at left to answer questions 22–27.
ECTC 0016C
22. To perform the test shown, should both connectors be connected? YES / NO
(Circle one)
23. These connectors are both: Male / Female (Circle one) 24. What type of measurement is called for in this step? (Check one) Circuit voltage measurement Circuit resistance measurement Circuit amperage measurement 25. In what position must the ignition switch be set? ON / OFF (Circle one) 26. What two terminals must be tested? _____ and _____ 27. Which side of the C/UNIT CONNECTOR must be tested? Terminal side / Harness side (Circle one)
6
Module 2
Refer to the illustration on the left to answer questions 28–33. 28. What type of measurement is being performed? (Check one) Check circuit voltage Check circuit resistance Check circuit amperage 29. What pedal is being applied? Brake / Accelerator (Circle one) 30. What is the color of the wire connected to terminal 1? ___________________________________ 31. Is this inspection done with the connector separated? YES / NO (Circle one) 32. What does ‘M107’ refer to? ___________________________________ 33. On which side of the connector should the meter be connected? Terminal side/Harness side (Circle one) You have just completed this worksheet. You should now be able to interpret wiring diagram symbols and answer related questions. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials _____________________ Return the workstation to the condition in which it was found. Module 2
7
Module 2
NOTES
8
Module 2
MEASURING A VAILABLE VOL TAGE AV VOLT
Objective:
Given a multimeter, a circuit simulator and a windshield wiper motor circuit, measure available voltage at different points in a circuit and make comparisons for the purpose of diagnosing faults.
Relevance: Voltage is electrical pressure. This electrical pressure is necessary to push current through a circuit. A voltmeter is used to measure voltage and can be very beneficial when used as a diagnostic tool for testing electrical malfunctions. Resources: • Digital multimeter • ESM • Circuit simulator Skill Check: You will build a circuit and test available voltage. You will locate and identify the windshield wiper motor circuit on a test vehicle and measure the available voltage.
Module 3
1
Module 3
1. ECTC 0016C
Using the drawing in figure 1, build the circuit on the simulator overlay. Use the parts provided to build this circuit. Switch the circuit ON to verify the load works, then switch it OFF.
Overlay #1 Switch on negative side of circuit
Figure 1
2.
Rotate the selector knob on the meter to select DC Volts (V ).
3.
Connect the red test lead to the V input jack and the black test lead to the COM (common) input jack.
Red Black
2
Module 3
4.
Connect the red test lead to the battery positive (+) terminal on the simulator and the black test lead to the battery negative (–) terminal on the simulator (Figure 2).
5.
Switch the circuit ON. Module 3
A
E
D C Figure 2
6. RECORD ANSWER
B
Measure available voltage at the battery, then record the reading at left.
Note: This measurement indicates the voltage available during circuit operation. Testing for adequate available voltage should be the first circuit measurement you make. This also confirms that the meter and test leads are in good working order. Battery voltage less than 12 volts indicates a potential problem.
Module 3
3
7. ECTC 0016C
RECORD ANSWER
Leave the black lead connected to the battery negative and move the red lead to the positive terminal of the load (Figure 2, position A ). With the switch still ON (closed), measure the voltage and record the reading in the space at left.
Note: This measurement indicates the voltage available at the load. This reading should be slightly less than measured in step 6. Low voltage readings indicate high resistance between the power supply and the load. Low voltage may result in false codes being stored in ECM-controlled circuits. A voltage reading close to the source voltage confirms continuity between the battery and the load, which means the wiring is good.
RECORD ANSWER
8.
Leave the black lead connected to the battery ground and move the red lead to the ground side of the load (Figure 2, position B ).
9.
Turn the circuit switch OFF (open switch) and measure the voltage on the ground side of the load. Record your answer at left. Based on this meter connection, is there voltage immediately after the load? ____________________________________ Is the load operating at this time? ________ Why do you think this is the case? ____________________________________ ____________________________________ ____________________________________
4
Module 3
RECORD ANSWER
10. Now close the switch (circuit ON) and record the voltmeter reading in the space at left. Instructor’s Initials _______________________
Module 3
11. Have your instructor assign a test vehicle for the following voltage measurement exercises. 12. Set up the meter to measure DC volts. RECORD ANSWER
Connect both meter leads to the battery and record the battery voltage at left. 13. With the ignition switch OFF, measure available voltage to all fuses. Note: On newer vehicles, all fuses are numbered in the fuse box. If you cannot read the numbers, use a flashlight or a drop light. Connect the black lead to ground and the red lead to each fuse in the fuse box. Is battery voltage available to all the fuses? YES / NO (Circle one) Why? ___________________________________ ___________________________________ Note: When testing circuit operation, refer to the appropriate wiring diagram to determine which switches (if any) must be ON before measuring available voltage.
Module 3
5
14. To test the windshield wiper motor circuit, switch the ignition ON (engine OFF) and measure available voltage to the windshield wiper motor.
ECTC 0016C
• Find the wiper motor wiring diagram in the EL section of the service manual. • Using this diagram, trace the wiper motor voltage feed wire from the wiper fuse to the wiper motor. 15. What color is this wire on the test vehicle? ___________________________________
RECORD ANSWER
16. Disconnect the connector, locate the wire terminal feeding this circuit, then measure and record the voltage in the space provided at left. Note: This reading should be about the same as the available battery voltage. By confirming that the wiper motor has voltage available, you know the fuse, wiring, connections and battery are in good working order ... up to the load. In other words, the source side of the circuit is okay. If a complaint of “wipers don’t work” were presented, the load and the ground path are the only things left to check. You have just completed this worksheet. You should now be able to measure available voltage at different points in a circuit and make comparisons for the purpose of diagnosing faults. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials _______________________ Return the workstation to the condition in which it was found.
6
Module 3
MEASURING VOL TAGE DROP VOLT
Objective:
Given a voltmeter, an Electrical Lighting Simulator and an assigned vehicle, measure voltage drop as specified and evaluate the results against established specifications.
Relevance: During circuit operation, it is normal for electrical loads to use up the bulk of the available voltage to make them operate. Circuit connections, wiring and grounds may also cause a nominal amount of voltage drop through each connection. By using a voltmeter to measure voltage drop at different points in a circuit, you can quickly isolate the part of the circuit that causes faulty circuit operation (e.g. loose, dirty or damaged connections). Resources: • Digital Multimeter • Test vehicle equipped with rear window defogger • Electrical Lighting Simulator Skill Check: You will measure the voltage drop in a lighting circuit. On a test vehicle, you will measure voltage drop in a rear window defogger circuit.
Module 4
1
Module 4
Use the Electrical Lighting Simulator to perform steps 1–8.
ECTC 0016C
1.
Switch the headlights ON.
2.
Measure available voltage at the source (battery voltage), by connecting the multimeter to the battery. Record the reading here. ____________ Volts
Headlamp bulb
+
––
Battery
Vehicle frame (body ground)
Test voltage drops as follows:
+
––
Battery
3.
Connect the red lead to the battery positive cable and the black lead to the source side of the headlamp (closest to battery).
4.
Switch the circuit ON and measure the voltage drop between these points. The voltage reading displayed on the meter is the voltage drop between the battery and the load. Record the reading here. ____________ Volts
Vehicle frame (body ground)
Note: Voltage drop must be measured with the circuit operating. When measuring voltage drop across a portion of the wiring, the voltage drop reading should be very small.
2
Module 4
5.
With the circuit still ON, move the black lead to the ground side of the load. Move the red lead to source side of the headlamp. Record the reading here. ____________ Volts
+
––
Battery
Note: This reading is the voltage drop across the load. This reading should be very close to source voltage. If it is not close to source voltage, there is high resistance at some other point in the circuit.
Vehicle frame (body ground)
6.
With the circuit still ON, measure voltage drop across the ground circuit as follows: • Move the red lead to the ground side of the same load and the black lead to the battery negative terminal.
+
––
• Record the reading here.
Battery
____________ Volts
Vehicle frame (body ground)
Module 4
3
Module 4
7. ECTC 0016C
RECORD ANSWER
Add the readings obtained in steps 3–6 and record the total here. _____________ Volts Does this value equal the reading obtained in step 2? YES / NO (Circle one) Should they be the same? YES / NO (Circle one)
Voltage Drop Chart
Note: The sum of the voltage drops in a circuit should equal the available source voltage. While a circuit is operating, the ground side voltage drop should be .1 volt or less.
Maximum Allowable Voltage Drop* Wire Connections
0.1 Volt or less for each connection
Ground connections
0.1 Volts
Switch contacts
0.3 Volts
Starter Solenoids
0.5 Volts
*These guidelines are not applicable to electronically-controlled circuits
4
A voltage drop greater than .1 volt may indicate lose, dirty or corroded connections or damage within the wiring harness between the circuit load and the battery negative cable connection. Instructor’s Initials _______________________
8.
Have your instructor assign you a test vehicle equipped with a rear window defogger system to practice measuring voltage drop.
9.
Switch the ignition and rear window defogger ON to activate the rear window defogger circuit.
Module 4
10. Measure available voltage at the source side of the load and record it here (see illustration at left). _______________ Volts 11. Is this reading acceptable?
+
––
Module 4 Rear window defogger
Battery
Vehicle frame (body ground)
YES / NO
(Circle one)
12. Measure voltage drop between the battery and the source side of the rear window defogger and record it here. _______________ Volts +
––
Battery
Rear window defogger
13. Look again at the voltage drop chart on page 4. Is this reading within specifications? YES / NO
(Circle one)
Vehicle frame (body ground)
Module 4
5
14. With the rear defogger circuit still operating, measure voltage drop across the entire rear window defogger grid and record the reading here.
ECTC 0016C
_______________ Volts
+
––
Rear window defogger
Battery
Vehicle frame (body ground)
Note: Simply looking at the brightness of a bulb, or listening to the speed of a motor, or feeling the warmth of a defogger gird will not tell you if any of these devices are operating as they normally should. Now that you know the voltage drop on the source side of the load as well as the voltage drop through the load, the only missing link is the ground side of the circuit.
15. With the circuit still ON, connect the red multimeter lead to the ground side of the defogger grid and the black lead to the negative battery cable. This connection will allow you to measure the voltage drop across the entire ground circuit for the defogger grid. The measured ground side voltage drop is: _______________ Volts
+
––
Battery
Rear window defogger
Vehicle frame (body ground)
6
Module 4
Note: A voltage drop measurement on the ground side of a circuit tests all of the following: • • • • •
Circuit connections within the wiring harness The connection at the body ground location for the defogger grid The frame of the vehicle The battery ground cable The connection at the battery post
Each of these listed points could be the root cause of a voltage drop. The challenge is to pinpoint the problem to the exact cause by following a logical sequence of diagnosing each part of the circuit and ruling out each part one at a time. 16. Now that you know the total voltage drops within the circuit, determine if anything could have been overlooked. Fill in the boxes below to verify the readings you just obtained.
Note Note: A weak battery or insufficiently charged battery will affect the results of a voltage drop test.
Module 4
7
Module 4
17. Now measure the available battery source voltage and compare with the total voltage drop measurements. Are they the same?
ECTC 0016C
YES / NO
(Circle one)
In summary, voltage drop testing is only partially effective unless you have all of the facts. You must know the available battery voltage to begin with, so you can compare all of the other voltage drop readings to this total. Keeping in mind the specifications in the chart at step 8, you should be able to determine if any of the readings are outside the normal operating range. By putting all these facts together with a solid customer concern, you should be able to effectively diagnose problems in faulty circuits. You have just completed this worksheet. You should now be able to measure voltage drop as specified and evaluate the results against established specifications. If you have any doubt about your skills in completing this worksheet, please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials _______________________ Return the workstation to the condition that you found it.
8
Module 4
MEASURING RESIST ANCE RESISTANCE
Objective:
Given a digital multimeter, a circuit simulator, a service manual, a fuelinjected vehicle and other components, measure resistance and compare to specifications.
Relevance: Electrical resistance opposes the flow of current in a circuit. Electrical accessories, also referred to as “loads”, use up most of the voltage in a circuit. Excessive circuit resistance causes the current flow to decrease. This results in faulty circuit operation. Resources: • Digital multimeter • Circuit simulator • Service Manual • Various electrical components • Fuel injected vehicle • Combination Switch Skill Check: Measure the resistance of various electrical components with a digital multimeter. Check continuity of a combination lighting switch.
Module 5
1
Module 5
1. ECTC 0016C
Place the overlay for circuit #1 on the simulator and build the circuit below. Do not connect to the battery.
Source wire
Switch
Overlay #1
2.
Connect the test leads to the meter jacks and switch the meter to “Ω.” Touch the test leads together and verify the readout is 0–0.3 Ohms (Continuity).
3.
Measure the resistance of the source wire. Readings of less than 1 Ohm are an exception.
Note: When using digital multimeters with autoranging capabilities, the meter automatically selects the most accurate range when you turn it ON. Most auto-ranging meters allow you to change the range or displayed value while the meter is in use.
2
Module 5
4.
Connect one of the ohmmeter leads to each of the switch terminals, then close the switch.
Note: Never use the ohmmeter to make any tests with power connected to the circuit being tested.This could damage the meter and give false readings. RECORD ANSWER
5.
Record the resistance (Ohms) you measured in step 4 in the space at left. Module 5
Note: Switch contacts should have very low resistance. 6.
What would cause high resistance across switch contacts? ___________________________________
RECORD ANSWER
7.
Measure and record the resistance of the following circuit components:
a.
Description: Load Resistance (Bulb) Record your answer in the space at left.
RECORD ANSWER
b.
Description: Resistance Across the Wires. Record your answer in the space at left.
8.
Add the resistance values just taken (steps 5–7) and record your answer below. This is the total circuit resistance. ____________Ohms, Total circuit resistance.
Module 5
3
9. ECTC 0016C
RECORD ANSWER
Connect additional simulator wires to the load and to the switch but do not connect to the battery. Measure the resistance, then record your answer in the space provided at left.
10. Does this reading equal the value in step 8? YES / NO (Circle one) 11. What could cause this reading to be different than the other reading? ___________________________________ ___________________________________ ___________________________________ 12. Ask your instructor to assign a test vehicle for the following exercises. RECORD ANSWER
13. Measure the resistance of four injectors. Record the resistance measurements below. #1
_________
#2
_________
#3
_________
#4
_________
14. How would the engine run if the resistance of each injector was significantly different? ___________________________________ ___________________________________
4
Module 5
Stop Instructor’s Initials ______________________ Have your instructor assign a vehicle for the following steps. TURN Right turn WIPER CONTROL FOG LAMP
1st
ON
OFF
N OFF
A
INT
Wash 2nd B
LO
OFF Left turn
C
HI
Lighting Switch* OFF A
B
1st C
A
B
2nd C
A
B
C
15. Using the vehicle service manual or ESM, complete the switch charts at left and bottom for the combination lighting, wiper and fog lamp switch you're measuring. Note: Depending on your vehicle, you may not use all chart positions. 16. Using the ohmmeter, check continuity for each switch position according to the charts. Record your results here. (Circle one)
Wiper Switch* OFF INT LO
HI
WASH
Lighting switch:
OK
Not OK
Wiper switch:
OK
Not OK
Fog lamp switch:
OK
Not OK
Turn signal switch:
OK
Not OK
Turn Signal Switch* R
N
L
Fog Lamp Switch* OFF ON
Module 5
5
Module 5
You have just completed this worksheet. You should now be able to measure resistance and compare it to specifications. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work.
ECTC 0016C
Instructor’s Initials ______________________ Return the workstation to the condition that you found it.
6
Module 5
MEASURING CURRENT
Objective:
Given a digital multimeter, a circuit test kit with overlay #1, measure current flow through a circuit and evaluate the results.
Relevance: Current is the flow of electrons in a circuit. Amperage, the measurement of current flow in a circuit, is affected by the resistance of the circuit load and the voltage applied to the circuit. Malfunctions such as low voltage, excessive circuit resistance or a faulty component reduce current flow which results in poor circuit operation. Batteries, starter motors and alternators operate under high current demands. When you suspect one of these is malfunctioning, measure the current flow in the circuit and compare it with specifications in the service manual. One of the more commonly overlooked reasons for testing current flow is to determine what causes a battery to go dead overnight. Resources: • Digital multimeter • Circuit Test Kit • Circuit Overlay #1 Skill Check: Measure current flow in a circuit with a multimeter. Measure parasitic load in a test vehicle battery.
Module 6
1
Module 6
1. ECTC 0016C
Follow the drawing on simulator overlay #1 and use the components provided to build the circuit. Switch the simulator ON to be sure the load works, then switch it OFF. CAUTION:
Never attempt to measure current flow in excess of 10 amps. Y ou could damage the meter You (possibly beyond repair) or melt the 10A fuse. To prevent damage to the meter or its fuse, be sure to connect the meter’s red test lead to the “10A “10A”” meter jack and the black test lead to the “COM” jack. 2.
Disconnect the source wire from the load.
3.
Connect the multimeter to the circuit as shown in the following illustration.
Overlay #1 Switch in negative side of circuit
2
Module 6
RECORD ANSWER
4.
Rotate the selector knob so the multimeter is in the DC Amps position.
5.
Press the switch on the circuit tester to activate the circuit and record the amperage reading at left.
Module 6
Module 6
6.
Switch the simulator OFF, disconnect the meter leads from the circuit, then reconnect the circuit wiring and meter as illustrated below.
7.
Make sure the selector knob on the multimeter is still in the DC Amps position.
3
ECTC 0016C
RECORD ANSWER
8.
Switch the simulator and circuit ON and record the amperage reading at left
Note: The amperage measured in a series circuit should be the same at any point in the circuit. 9.
Were the two amperage readings taken in steps 5 and 8 about the same? YES / NO
(Circle one)
Instructor’s Initials ______________________
Measure Parasitic Load Have your instructor assign a vehicle for the following steps. 10. Using an assigned vehicle, measure the parasitic load on a battery. 11. Check to see that all circuits and the ignition switch are OFF. 12. Disconnect the negative battery cable and connect the multimeter in series between the battery post and battery cable.
4
Module 6
13. With the meter still set up to read amperage, what is the reading? __________________ A Note: In most cases, parasitic draw should be less than 30 mA if the vehicle is operating normally. Readings in excess of that typically indicate a problem. On cars equipped with BCM, a momentary high current drain above 150 mA will occur, but after 30 seconds, the reading should drop below 30 mA. 14. Switch the meter OFF, then disconnect it from the battery. 15. Reconnect the battery cable. You have just completed this worksheet. You should now be able to measure current flow through a circuit and evaluate the results. If you have any doubt about your skills in completing this worksheet, please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials ______________________ Return the workstation to the condition that you found it.
Module 6
5
Module 6
NOTES
6
Module 6
COMBINA TION SWIT CH OPERA TION COMBINATION SWITCH OPERATION
Objective Objective:
Given a combination switch and a combination switch circuit, read a combination switch chart and diagnose various combination switch circuits using a digital multimeter.
Sample Combination Switch
Relevance: A combination switch contains multiple switches. Each multiple switch uses a single control lever to control several circuits. In order to diagnose a malfunction in one or more related circuits you must understand how the switch works and how it controls the various circuits. Resources: Combination light switch Skill Check: Identify the terminal contacts in a combination light switch. Identify circuit connections and current paths in a lighting circuit.
Module 7
1
Module 7
TURN Right turn
ECTC 0016C
FOG LAMP
OFF N
ON
1st A
INT
WASH B
2nd LO
OFF C
Left turn HI
Figure 1
Refer to Figure 1 and the switch chart for steps 1–3. 1.
Switch Positions
The combination switch (Figure 1) controls the parking lights, high and low beam headlamps, turn signals, windshield wipers and windshield washer. Study the switch chart at left and Figure 1. How many light switch positions are there? ___________________________________ How many wiper positions are there?
Line indicates continuity
___________________________________ 2.
Connector (terminal) numbers Lighting Switch Chart, Sample
There are two types of illustrations in the service manual that describe the operation of the combination switch: • •
3.
Charts Wiring Diagram
A Combination Switch Chart, like the one on the left, illustrates the following: • • •
Terminal numbers Switch positions Continuity indicators (the lines between circles)
Which terminals are connected when the switch is positioned in 2B? ___________________________________
2
Module 7
The wiring diagrams on the following page (Figures 2 and 3) illustrate the circuits attached to a hazard switch. The light switch wiring diagrams shown contain the following information: •
Voltage source for the switch.
•
Switch terminal numbers
•
Wiring that connects the circuit components.
Answer the following questions which refer to the electrical diagrams on the following page (Figures 2 and 3). 4.
Which fuses connect the battery to the hazard switch? ____________________________________
5.
What are the connector numbers for the front turn signal lamps? ____________________________________
Component
Terminal
6.
Study Figures 2 and 3 on the following page. Based on these wiring diagrams, locate the hazard switch, then record the switch terminal numbers for the circuits listed at left.
7.
What is the harness connector number at the hazard switch?
Combination Flasher Multi-Remote Control Relay-2 Turn Signal Lamp, RH Combination Meter (Turn Signal Lamp), LH Ignition Switch Battery power
___________________________________
Module 7
3
Module 7
Figure 2
Figure 3
ECTC 0016C
4
Module 7
8.
Identify the harness connector numbers at the rear turn signal lamps. ___________________________________
9.
Identify and describe the fuses that protect the Turn Signal and Hazard Warning Lamp circuits. ___________________________________ ___________________________________
Note: An electrical schematic does not show the detail found in a “wiring diagram,” but the entire circuit is displayed on a single page. This avoids having to follow the circuit through several pages to trace a circuit or a wire. Not all electrical circuits have a schematic diagram. For those that are available, they will help you understand how the circuit operates. A System Description usually accompanies the schematic to describe power distribution within the circuit.
Module 7
5
Module 7
Answer the following questions about the Turn Signal Circuit using the Turn Signal Operation information and schematic diagram (Figure 4).
ECTC 0016C
10. From the system description, identify which fuse powers the hazard switch: #________
Fuse rating: _______A
11. From what terminal on the Combination Flasher Unit does current enter from the Hazard switch? Terminal ________ 12. Identify the circuit path (in sequence) from the hazard switch to the rear combination lamp, LH and ground when the turn signal switch is in the LEFT TURN position. Letter
Part Name
____
________________________
____
________________________
____
________________________
____
________________________
____
________________________
____
________________________
____
________________________
13. Starting from the LH front turn signal lamp, trace the circuit back to the source. 14. Identify the letter that indicates where the LH turn signal circuit becomes a parallel circuit. _____________
6
Module 7
Module 7
M
B
C F
A
L
O K
N E
H
D I
G J
Figure 4
Module 7
7
Use the wiring diagram on page 9 (Figure 5) to answer the following questions:
ECTC 0016C
15. What is the fuse number and rating for the combination switch circuit? #________
Fuse rating: _______A
16. What does the black dot at 1 represent? _________________________ 17. Does 2 receive “switched” power or constant battery power? ____________________ 18. How much voltage should be at 3 in the “OFF” position? _________________________ 19. How much voltage should be at 4 with the ignition switch OFF? _________________________ 20. How much voltage should be 5 with the Fog Lamp Switch ON? _________________________ 21. What happens to the front fog lamps if there is an open circuit at 6 ? LH lamp__________________ RH lamp__________________
8
Module 7
1
2 4
5
Module 7
3
6
Figure 5
Module 7
9
You have just completed this worksheet. You should now be able to read a combination switch chart and diagnose various combination switch circuits using a digital multimeter. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work.
ECTC 0016C
Instructor’s Initials _______________________ Return the workstation to the condition in which it was found.
10
Module 7
DIAGNOSING ONE TRANSFER (1T) RELA Y MALFUNCTIONS RELAY
From voltage source
Objective:
To hood switch To starter circuit Sample 1T relay 1-T
Given a service manual or ESM, a digital multimeter, a one transfer (1T) relay and circuit test kit w/overlay #2, diagnose the operation of a 1T relay.
Relevance: Unwanted circuit resistance can cause abnormal voltage drops. Abnormal voltage drops can lead to customer complaints relating to faulty circuit operation. Poor connections or corrosion may be the root cause of the high resistance. A voltmeter can be used to analyze the circuit while in operation to help locate the fault. Resources: • Circuit Test Kit w/overlay #2 • Digital Multimeter • 1T Relay Skill Check: Predict and measure available voltage at the terminals of a 1T relay.
Module 8
1
Module 8
ECTC 0016C
Switch Open Test P oint Point
Voltage, predicted
Terminal 1 A
Predicted V oltage Voltage 1.
Before you build the circuit shown on simulator overlay #2, predict the voltage level at each of the terminals.
Terminal 2 B
Examine the top of the relay and the simulator overlay to identify the terminal numbers.
Terminal 3 C Terminal 4 D
a.
Assume the black lead of the multimeter is connected to ground and the red lead touches the terminals listed in the charts.
b.
First, assume the coil control switch is Open, then assume it is Closed Closed. Open
Terminal 5 E
Switch Closed Test P oint Point Terminal 1 A
Voltage, predicted
Record your predicted voltage readings in the charts at left.
Terminal 2 B Terminal 3 C Terminal 4 D Terminal 5 E
Overlay #2
2
Module 8
Measured V oltage Voltage
RECORD ANSWER
a. Switch Open Test P oint Point
Voltage, measured
2.
Use the 1-Transfer Relay and the attached jumper wires to build the circuit shown on overlay #2.
3.
Plug in the simulator and switch the circuit ON. Using the multimeter, measure and record the battery voltage in the space at left.
4.
Measure relay voltages on Circuit No. 2 as follows:
Module 8
Connect the black lead of the multimeter to ground, then touch the red test lead to the harness side of each terminal and measure the voltage.
Terminal 1 A Terminal 2 B Terminal 3 C Terminal 4 D Terminal 5 E
b. Switch Closed Test P oint Point Terminal 1 A Terminal 2 B Terminal 3 C Terminal 4 D Terminal 5 E
Module 8
a.
Measure with the coil control switch open open.
b.
Measure with the coil control switch closed. closed
Record the readings at left.
Voltage, measured
Note: If a relay “buzzes,” current flow through the coil control circuit may be too low to keep the contact circuit closed. This failure occurs if the source voltage is below specifications or if the circuit resistance is too great. The coil control winding inside the relay should be the only significant resistance in the circuit.
3
5.
Your voltage measurements should match the predictions in step 1. If not, review your predictions and determine why you were incorrect.
6.
Examine the Antilock Brake System (ABS) circuit diagram (Figure 1) on the next page and answer the following questions:
ECTC 0016C
Two relays are illustrated in the circuit diagram. Which one is a 1T relay? ___________________________________ 7.
What type of relay is the other relay? ___________________________________
8.
Which terminal of the IT relay provides source voltage to the coil control circuit? ___________________________________
9.
What terminal number of the ABS control unit is connected to the source voltage of both relay control coils? ___________________________________
4
Module 8
Antilock Brake System
Module 8
Figure 1
Module 8
5
10. What must happen at terminal 6 of the ABS Control Unit so battery voltage is supplied to the ABS solenoid valves? (Check one)
ECTC 0016C
_____ Provide battery voltage to terminal 6. _____ Provide ground at terminal 6. Instructor’s Initials ______________________ Ask your instructor to assign you a test vehicle and circuit. Use the Starting System Simulator for the remaining steps. 11. Verify relay operation by operating the circuit. RECORD ANSWER
12. Remove the relay and use a voltmeter to test for voltage at the coil control circuit, then record the voltage reading at left. Note: A One Transfer Relay has a coil control circuit and two contact point circuits. Each circuit must be diagnosed separately. During diagnosis, remember to turn ON any switches required to operate the circuit. Refer to the wiring diagram for the circuit you are testing. 13. If there is no voltage, diagnose the coil control circuit between the relay socket and the voltage source. Refer to the wiring diagram and choose test points that are easy to locate that will help you quickly isolate the problem.
6
Module 8
14. Connect the red lead to the positive post of the battery and touch the black lead to the control circuit ground terminal at the relay connector socket. If there is no ground at the socket the meter will read zero volts. If the meter reads 12 volts, the control coil ground is good. Select test points that are easy to find and check, and look for loose, dirty or damaged connections to determine why the ground is faulty. 15. Use a fused jumper wire between terminal 3 and 5 in the relay socket to test operation of the circuit controlled by the relay. Caution: Never bypass the coil winding with a jumper. Doing so may damage the wiring harness and/or control switches. 16. If the circuit does not work with the fused jumper installed, • there may be no source voltage at terminal #3 • there may be an open between terminal #5 and the load. • the ground for the load may be open. 17. Use the same procedure to test the normally closed contact point circuit by jumping terminals #3 and #4 at the relay socket. Does the load in this circuit operate? YES / NO
(Circle one)
You have just completed this worksheet. You should now be able to diagnose the operation of a one transfer (1T) relay. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials ______________________
Module 8
Return the workstation to the condition that you found it. 7
Module 8
NOTES
8
Module 8
DIAGNOSING ONE MAKE (1M) RELA Y MALFUNCTIONS RELAY
Objective:
Given overlay #3, a service manual, and test equipment, test a vehicle with a 1M relay circuit.
Relevance: A one make (1M) relay contains a load circuit and a control circuit. The load circuit is completed when an external switch in the control circuit closes. In the example, terminals 1 and 3 are connected to source voltage. Terminal 5 connects to the load circuit and terminal 2 connects the control circuit to ground. When terminal 2 is grounded, the contacts close, completing the circuit through terminal 5 to the load. Circuit malfunctions can be caused by a faulty relay, circuit wiring and connectors or the actual load itself. To be effective at diagnosing 1M relay malfunctions, you must understand relay operation. Resources: • Digital Multimeter • Simulator w/overlay #3 • Service manual Skill Check: Use a multimeter to test the operation of a circuit controlled by a 1M relay.
Module 9
1
Module 9
Predicted V oltage Voltage
Switch Open
ECTC 0016C
Test P oint Point
Voltage Predicted
Terminal 1
A
Terminal 2
B
Terminal 3
C
Terminal 5
D
1.
Examine the top of the relay and the simulator overlay to identify the terminal numbers. Assume the black lead of the multimeter is connected to ground and the red lead touches each test point listed in the chart. First, assume the coil control switch is OPEN, then assume it is CLOSED.
Switch Closed Test P oint Point
Voltage Predicted
Terminal 1
A
Terminal 2
B
Terminal 3
C
Terminal 5
D
Before you build the circuit shown on simulator overlay #3, predict the voltage levels at each of the terminals.
Record the predicted voltage readings in the spaces provided at left.
D C A B
Overlay #3
2
Module 9
Measured V oltage Voltage
RECORD ANSWER
2.
Plug in the simulator, then measure and record the source voltage at left.
3.
Measure relay voltages as follows:
Switch Open Test P oint Point
a.
Voltage Measured
Terminal 1
A
Terminal 2
B
Terminal 3
C
Terminal 5
D
Switch Closed Test P oint Point
Voltage Measured
Terminal 1
A
Terminal 2
B
Terminal 3
C
Terminal 5
D
Use a 1 Make Relay to build the circuit shown on overlay #3. Attach the black multimeter lead to ground, then touch the red lead to each of the numbered terminals.
b.
Measure actual voltages at each of the relay terminals.
c.
First, measure with the coil control switch OPEN, then measure with the coil control switch CLOSED.
Record the measured voltage in the spaces provided.
4.
Are the voltage measurements in step 3 the same as your predictions in step 1? YES / NO (Circle one)
Module 9
3
Module 9
Theft W arning Relay Warning
ECTC 0016C
Test P oint Point
5.
Voltage Predicted
Terminal
1
Terminal
2
Terminal
3
Terminal
4
Terminal
5
Assume the ignition switch is in the START position, the clutch interlock switch is in the released position, and the Theft Warning Relay control circuit is not grounded. Record the voltages you expect to measure at each of the theft warning relay terminals. 6.
Clutch Interlock Relay Test P oint Point
Voltage Predicted
Terminal
1
Terminal
2
Terminal
3
Terminal
5
Now, assume the ignition switch is in the START position, the clutch interlock switch is still released. Record the voltages you expect to measure at each of the clutch interlock relay terminals.
Diagnostic Strategy After verifying a customer complaint (symptom), the most efficient way to diagnose relay circuit malfunctions is to understand how the circuit should operate.
7.
4
Refer to the Starting System Wiring Diagram (Figure 1) to answer the following questions.
•
Check for voltage on both sides of each fuse
•
Locate and test for voltage at the circuit relays and switches.
•
Operate the circuit while touching and/or listening to each relay in the circuit. You should be able to feel or hear the contacts close.
•
Substitute a known good battery and retest circuit operation.
•
Look for loose ground connections.
As you have seen in this exercise, proper relay operation is often affected by external malfunctions in the circuit. Don’t jump to conclusions.
Module 9
Module 9
Figure 1
Module 9
5
ECTC 0016C
Blower Motor Relay:
Any V ehicle Vehicle
Fuel Pump Relay:
Any V ehicle Vehicle
Ignition Relay:
Any V ehicle Vehicle
Radiator Fan Relays:
Any V ehicle Vehicle
8.
Select one of the relay circuits at left to test on the assigned vehicle: Record the following information: Vehicle model: ______________________ Vehicle year: _______________________
9.
What system are you working on? ___________________________________
10. Refer to the wiring diagram for the circuit you are testing. 11. The coil control circuit and relay contact point circuits are two separate circuits. Diagnose them separately. 12. The circuit must be ON to test for voltage. 13. To check operation of the contact circuit, connect a fused jumper wire to terminals #3 and #5 in the relay socket. These contacts normally close when the relay energizes. The load should operate. Does the load operate? YES / NO (Circle one) RECORD ANSWER
14. If the load does not operate, test for available voltage at terminal #3 in the relay socket, then record the voltage reading at left. 15. If there is no voltage at terminal #3, test for voltage at various places between the battery and the relay. Use the wiring diagram to select points that are easy to test to isolate the malfunction quickly.
6
Module 9
RECORD ANSWER
16. Test for available voltage to the coil control circuit, then record the voltage reading at left. 17. If there is no voltage at the coil, test for voltage at various places between the battery and the relay. Use the wiring diagram to select points that are easy to test to isolate the malfunction quickly. 18. Connect the red meter lead to the positive battery post and the black lead to the coil control circuit ground terminal in the relay socket. 19. What is the meter reading? ____________________________________ 20. What does this indicate about the circuit? ___________________________________ Note: If the meter reading obtained is zero (0) volts, the circuit is open between the relay socket and ground. If the coil control ground is computer-controlled, switch the circuit ON to ensure the control unit is trying to supply ground. You have just completed this worksheet. You should now be able to test a vehicle with a 1M relay circuit. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials ______________________ Return the workstation to the condition that you found it.
Module 9
7
Module 9
NOTES
8
Module xx
DIAGNOSING TWO MAKE (2M) RELA Y MALFUNCTIONS RELAY
to fuse #1
to fuse #10
to fuse #4
Objective:
Given a service manual, a digital multimeter, a Two Make (2M) relay and a circuit test kit with overlay #4, diagnose the operation of a 2M relay.
Relevance: A 2M relay contains two load circuits and a control circuit. The load circuits are completed when an external switch in the control circuit closes. Sample 2M relay
Circuit malfunctions can be caused by a faulty relay, circuit wiring and connectors or the actual load itself. To be effective at diagnosing 2M relay circuit faults, you must understand relay operation. Resources: • Digital multimeter • Assigned vehicle • Circuit Test Kit w/overlay #4 • 2M Relay
Module 10
Skill Check: Use a multimeter to test the operation of a circuit controlled by a 2M relay.
Module 10
1
ECTC 0016C
Predicted V oltage Voltage
Switch Open Test P oint Point
Voltage Predicted
Terminal 1
A
Terminal 2
B
Terminal 3
C
Terminal 5
D
Terminal 6
E
Terminal 7
F
1.
Examine the top of the relay and the simulator overlay to identify the terminal numbers. Assume the black lead of the multimeter is connected to ground and the red lead touches each test point listed in the chart. First assume the coil control switch is OPEN, then assume it is CLOSED.
Switch Closed Test P oint Point
Record the predicted voltage readings in the spaces provided.
Voltage Predicted
Terminal 1
A
Terminal 2
B
Terminal3
C
Terminal 5
D
Terminal 6
E
Terminal 7
F
Before you build the circuit shown on simulator overlay #4, predict the terminal voltages in the 2M relay circuit.
D
C E F
A B
Overlay #4 Schematic 2
Module 10
Measured V oltage Voltage
RECORD ANSWER
Switch Open Test P oint Point
2.
Plug in the simulator, then measure and record the source voltage at left.
3.
Measure relay voltages as follows:
Voltage Measured
Terminal 1
A
Terminal 2
B
Terminal 3
C
Terminal 5
D
Terminal 6
E
Terminal 7
F
b.
Attach the black multimeter lead to ground, then touch the red test lead to each of the numbered terminals.
c.
Measure actual voltages at each of the relay terminals.
d.
First, measure with the coil control switch OPEN, then measure with the coil control switch CLOSED.
Voltage Measured
Terminal 1
A
Terminal 2
B
Terminal 3
C
Terminal 5
D
Terminal 6
E
Terminal 7
F
Module 10
Use a 2M Relay to build the circuit shown on the overlay.
Record the measured voltages in the spaces provided.
Switch Closed Test P oint Point
a.
4.
Are the voltage measurements in step 3 the same as your predictions in step 1? YES / NO
(Circle one)
3
Module 10
5. ECTC 0016C
Answer the following questions about the 2M Multi-Remote Control Relay-1 in the Turn Signal and Hazard Warning Lamp circuit (Figure 1). Situation: When the hazard switch is ON (closed) the hazard lamps remain OFF. How can you test the relay to determine if the malfunction is in the relay coil circuit or the contact circuit? Select the best answer:
4
a.
With the relay removed, connect a fused jumper wire between relay sockets 3 and 5, then observe the turn signal lamps. The left hand lamps should illuminate.
b.
With the relay removed, jumper relay socket 6 and 7 and observe the turn signal lamps. The right hand lamps should illuminate.
c.
With the relay removed, jumper relay socket 1 and 2 and observe the lamp.
d.
Choices a and b are both correct.
Module 10
Module 10
Figure 1
Module 10
5
6. ECTC 0016C
Answer the following questions using the attached Rear Window Defogger wiring diagram (Figure 2) and the service manual description. Identify the relay in the wiring diagram. Relay name Type NO/NC Case color __________________________________
7.
The Smart Entrance Control Unit controls the ground for the Rear Window Defogger Relay. Refer to the wiring diagram for this circuit and check all of the following that apply. Assuming fuse #1 is good, voltage is available at terminal 11 at all times when the ignition switch is ON. On cars without power door locks, voltage to terminal 1 at the rear window defogger switch comes from terminal 3 of the defogger timer. If fuse #9 fails during operation of the rear defogger, a 30 amp fuse should be used to replace it.
8.
With the Rear Window Defogger Switch ON (closed), what should the voltage reading be at terminal 11 of the Smart Entrance Control Unit? Battery voltage, 12 volts Battery ground, 0 volts
9.
With the Rear Window Defogger Switch ON (closed), what should the voltage reading be at terminal 20 of the Smart Entrance Control Unit? Battery voltage, 12 volts Battery ground, 0 volts
6
Module 10
Figure 2
Module 10
Module 10
7
ECTC 0016C
Smart Entrance Control Unit Test P oint Point
Voltage Predicted
Terminal 36 Terminal 10 Defogger Relay Test P oint Point
10. Based on the circuit in Figure 2, assume the ignition switch and Defogger Switch are both ON. Record the voltages you expect to measure at each of the Defogger circuit terminals in the charts at left. 11. What is the primary reason for using a 2M relay in the Defogger Circuit? (Circle one)
Voltage Predicted
a.
Due to the function of this circuit, there is a need to control each circuit independently. For example, power to the indicator lamp can be controlled independently by the defogger switch.
b.
Due to the high current demands placed on this relay there is the danger that a single set of relay contacts might be damaged or burned.
Terminal 1 Terminal 2 Terminal 3 Terminal 5 Terminal 6 Terminal 7 Defogger Switch Test P oint Point
Voltage Predicted
Terminal 1 Terminal 2
Instructor’s Initials ______________________ Terminal 3 Terminal 4 Terminal 5 Terminal 6
8
Shop Exercise Ask your instructor to assign you a test vehicle. 12. Select one of these relay circuits to test on the assigned vehicle. •
Rear Defogger relay
•
Theft Warning relay
Module 10
13. Record the following information: Vehicle model: ______________________ Vehicle year: ________________________ 14. Which of the above circuits did you select? ___________________________________ 15. Refer to the wiring diagram for the circuit you are testing. 16. Switch the circuit ON when diagnosing circuits. RECORD ANSWER
17. Remove the relay from its connector and test for available voltage at the coil control circuit socket. Record the voltage at left. 18. If there is no voltage at this location, test for voltage at selected points between the battery and relay. Use the wiring diagram to select points that are easy to test in order to isolate the problem quickly. 19. Switch the defogger ON.
Module 10
20. Connect the red multimeter lead to the positive battery post and the black lead to the coil control circuit ground terminal to verify a good ground, then record the voltage reading: ___________________________________ Based on this reading, do you think the ground circuit is good? YES / NO
Module 10
(Circle One)
9
21. The 2M Relay has two contact circuits. ECTC 0016C
RECORD ANSWER
•
To test them, remove the relay from the socket and connect socket terminals #3 and #5 with a fused jumper lead. The load should operate.
•
Jump terminals #6 and #7 with the fused jumper lead. The load should operate.
22. If the load does not operate in either case, use the wiring diagram to determine which terminal numbers receive voltage for the contact circuits. Use the voltmeter to test for voltage at the terminals for the contact circuits in the relay socket. Record the readings in the space at left. 23. If voltage is not present, diagnose each contact circuit between the relay socket and the voltage source by testing for voltage at selected test points. Use the wiring diagram to select points that are easy to test in order to isolate the problem quickly. You have just completed this worksheet. You should now be able to diagnose the operation of a 2M relay. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials ______________________ Return the workstation to the condition that you found it.
10
Module 10
DIAGNOSING ONE MAKE-ONE BREAK (1M-1B) RELAY MALFUNCTIONS
Objective:
Sample 1M-1B Relay
Given a test kit with overlay #5, a service manual, digital multimeter and a One Make-One Break (1M-1B) Relay, diagnose the operation of a 1M-1B relay.
Relevance: A One Make-One Break (1M-1B) relay contains two load circuits and a control circuit. Each load circuit is alternately powered depending on whether the control circuit is energized or not. Circuit malfunctions can be caused by a faulty relay, circuit wiring, connections or the load. To repair a circuit containing a 1M-1B relay you should understand how this type of relay operates. Resources: • Digital multimeter • Circuit Test Kit w/overlay #5 • Test vehicle • 1M-1B relay • Starter simulator
Module 11
Skill Check: Use a multimeter to test the operation of a circuit controlled by a 1M-1B relay.
Module 11
1
Predicted V oltage Voltage
Switch Open
ECTC 0016C
Test P oint Point
Voltage Predicted
Terminal 1
A
Terminal 2
B
Terminal 3
C
Terminal 4
D
Terminal 6
E
Terminal 7
F
1.
Before you build the circuit shown on simulator overlay #5, predict the voltage levels at each of the terminals. Examine the top of the relay and the simulator overlay to identify the terminal numbers. To do this, assume the black multimeter lead is connected to ground and the red lead touches each of the test points to the left. First, assume the coil control switch is open, then assume it is closed.
Switch Closed Test P oint Point
Voltage Predicted
Terminal 1
A
Terminal 2
B
Terminal 3
C
Terminal 4
D
Terminal 6
E
Terminal 7
F
D
C E
F
A B
Overlay #5 Schematic
2
Module 11
Measured V oltage Voltage
RECORD ANSWER
Switch Open Test P oint Point
2.
Plug in the simulator, then measure and record the source voltage in the space at left.
3.
Use the 1M-1B relay and build the circuit shown on overlay #5. Then attach the black meter lead to ground. Touch the red test lead to each of the terminals in the charts at left.
4.
Measure relay voltages on Circuit No. 5 (1M-1B Relay) with the coil control switch open and record the readings at left.
Voltage Measured
Terminal 1
A
Terminal 2
B
Terminal 3
C
Terminal 4
D
Terminal 6
E
Terminal 7
F
Module 11
Switch Closed Test P oint Point
Voltage Measured
Terminal 1
A
Terminal 2
B
Terminal 3
C
Terminal 4
D
Terminal 6
E
Terminal 7
F
Module 11
5.
Next, measure voltages with the coil control switch closed, then record the readings at left.
6.
Are the measured readings the same as your predictions (step 1)? YES / NO (Circle one)
3
ECTC 0016C
4
B
C
E
A
D
Module 11
Schematic Figure 1
7.
Examine the Automatic Speed Control Device (ASCD) circuit diagram in figure 1 and answer the following questions: There are five relays in the circuit diagram. Using the text section as reference, record the name and relay type (1T, 1M, 2T, etc.), whether it is NO or NC and the relay case color.
Relay name
T ype Type
NO/NC
Case color
A B C
D E
8.
Which position must the inhibitor switch be in to connect source voltage (through the inhibitor relay) to terminal 5 of the ASCD control unit? ___________________________________ Module 11
___________________________________ 9.
Which relay connects the voltage source to the normally closed contacts of the Inhibitor Relay? ___________________________________ ___________________________________
10. Which ASCD Main Switch position is used to complete the circuit to the normally closed contacts of the Inhibitor Relay? OFF / ON
Module 11
(Circle one)
5
11. Select the inhibitor relay to diagnose on the test vehicle.
ECTC 0016C
Instructor’s Initials ______________________ 12. Ask your instructor to assign you a test vehicle and circuit. 13. Check the operation of the load controlled by this relay. Does the load operate? YES / NO RECORD ANSWER
(Circle One)
14. If the load does not operate, remove the relay and test for available voltage at terminal 1 in the relay socket and record the reading at left. 15. If there is no voltage, test for voltage at different points between the source and the control circuit. Using the wiring diagram, locate the most efficient test points. Note: Diagnose malfunctions in the control coil ground circuit: Using an ohmmeter An ohmmeter checks the continuity of the circuit. Using a voltmeter A voltmeter tests for voltage at different points in the circuit while it is operating. While the circuit is grounded, there should be almost zero volts.
6
Module 11
16. If there is voltage at terminal #1, use a fused jumper between socket terminal 6 and 7 and try to operate the load again. Does the load in this circuit operate? YES / NO (Circle one) 17. If the load still does not operate, test for voltage at the terminals for the contact point circuit in the relay socket. Use the wiring diagram to determine which terminals should be connected to source voltage. Record the meter readings in the space provided at left. RECORD ANSWER
18. If there is no voltage available, test for voltage at points that are easy to locate to help you quickly isolate the problem. You have just completed this worksheet. You should now be able to diagnose the operation of a 1M-1B relay. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Module 11
Instructor’s Initials ______________________ Return the workstation to the condition that you found it.
Module 11
7
NOTES
8
Module xx
CIRCUIT DIAGNOSIS EXERCISE: #1
Objective:
Given a customer’s repair order, a service manual and a digital multimeter, verify, isolate, repair and recheck the fault in question.
Relevance: Circuit diagnosis is a critical part of making effective repairs. In this exercise you will be given a customer concern. The symptom applies to a vehicle which you must repair. You must verify, isolate, repair and recheck the cause of the malfunction using the customer repair order, vehicle service manual, appropriate test equipment, and all diagnosis skills. Resources: • Assigned vehicle • Electronic Service Manual • Digital Multimeter Skill Check: Vehicle electrical fault repaired and circuit operation verified by instructor after repair. When performing diagnostic procedures the following items should always be followed: 1. Verify the complaint 2. Isolate the cause 3. Repair the fault 4. Recheck your repair
Module 12
1
Module 12
ECTC 0016C
Customer Concern:
“Engine overheats. Customer uses A/C, engine overheats quickly when outside temp. is hot”
Cause:
Corrective Action:
Figure 1
2
Module 12
1.
Record the following information here and on the repair order (figure 1). Vehicle model: ______________________ Model year: ________________________
2.
Background information for Diagnosis #1: Customer Concern: Engine overheats Repair History: On 7/5, thermostat was replaced, but repairs were not verified. On 7/8, the radiator cap was replaced and coolant level topped off. Car was towed in two days later for same symptom.
3.
Module 12
With a teammate, think of all the possibilities for this incident. On the following page, list all of the possible causes for this overheating condition. If you have difficulty recalling all of the possible causes, you may use any diagnostic resources within the classroom to help you build your list. Once your list is complete to your satisfaction, rank the causes in the order of most probable. In other words, number them in the order you would test them.
3
Module 12
Possible Causes (List all possible causes for the given symptoms)
ECTC 0016C
________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________
4
Module 12
4.
After completing step 3, discuss your strategy with the instructor.
5.
With the instructor’s approval, verify, isolate, repair and recheck the fault in the order you ranked them in step 3. Perform all tests necessary to verify each possible cause.
6.
During your diagnosis, list below the results of your findings for each of the items you check from the list you created. Item tested: Actual vehicle results: 1st _____________________________ 2nd _____________________________ 3rd _____________________________ Additional items tested: ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ Module 12
________________________________ ________________________________ 7.
Module 12
When you have repaired the problem on the vehicle and verified the repair, record the cause and corrective action on the repair order (page 2).
5
As a result of this exercise, you should see the need for effective diagnostic skills and the benefit of taking your time to follow repair procedures and get the problem resolved before returning the vehicle to the customer.
ECTC 0016C
You have just completed this worksheet. You should now be able to verify, isolate, repair and recheck the fault in question. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials ______________________ Return the workstation to the condition that you found it.
6
Module 12
CIRCUIT DIAGNOSIS EXERCISE: #2
Objective:
Given a customer’s repair order, a service manual and a digital multimeter, verify, isolate, repair and recheck the fault in question.
Relevance: Circuit diagnosis is a critical part of making effective repairs. In this exercise you will be given a customer concern. The symptom applies to a vehicle which you must repair. You must verify, isolate, repair and recheck the cause of the malfunction using the customer repair order, vehicle service manual, appropriate test equipment, and all diagnosis skills. Resources: • Assigned vehicle • Electronic Service Manual • Digital Multimeter Skill Check: Vehicle electrical fault repaired and circuit operation verified by instructor after repair. When performing diagnostic procedures the following items should always be followed: Module 13
1. Verify the complaint 2. Isolate the cause 3. Repair the fault 4. Recheck your repair
Module 13
1
ECTC 0016C
Customer Concern:
Cause:
Corrective Action:
Figure 1
2
Module 13
1.
Record the following information here and on the repair order (Figure 1). Vehicle model: ______________________ Model year: ________________________
2.
Background information for Diagnosis #2: Customer Concern: Customer claims that it takes a long time to clear the rear window using the defogger circuit. Repair History: Checked voltage drop across rear window grid. Voltage appeared to be in the normal range. Replaced rear window defogger relay, but did not validate the repair.
3.
With a teammate, think of all the possibilities for this incident. On the following page, list all of the possible causes for this defogging condition. If you have difficulty recalling all of the possible causes, you may use any diagnostic resources within the classroom to help you build your list. Once your list is complete to your satisfaction, rank the causes in the order of most probable. In other words, number them in the order you would test them.
Module 13
Module 13
3
Possible Causes (List all possible causes for the given symptoms)
ECTC 0016C
________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________
4
Module 13
4.
After completing step 3, discuss your strategy with the instructor.
5.
With the instructor’s approval, verify, isolate, repair and recheck the fault in the order you ranked them in step 3. Perform all tests necessary to verify each possible cause.
6.
During your diagnosis, list below the results of your findings for each of the items you check from the list you created. Item tested: Actual vehicle results: 1st _____________________________ 2nd _____________________________ 3rd _____________________________ Additional items tested: ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________
7.
Module 13
Module 13
When you have repaired the problem on the vehicle and verified the repair, record the cause and corrective action on the repair order (page 2).
5
As a result of this exercise, you should see the need for effective diagnostic skills and the benefit of taking your time to follow repair procedures and get the problem resolved before returning the vehicle to the customer.
ECTC 0016C
You have just completed this worksheet. You should now be able to verify, isolate, repair and recheck the fault in question. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials ______________________ Return the workstation to the condition that you found it.
6
Module 13
CIRCUIT DIAGNOSIS EXERCISE: #3
Objective:
Given a customer’s repair order, a service manual and a digital multimeter, verify, isolate, repair and recheck the fault in question.
Relevance: Circuit diagnosis is a critical part of making effective repairs. In this exercise you will be given a customer concern. The symptom applies to a vehicle which you must repair. You must verify, isolate, repair and recheck the cause of the malfunction using the customer repair order, vehicle service manual, appropriate test equipment, and all diagnosis skills. Resources: • Assigned vehicle • Electronic Service Manual • Digital Multimeter Skill Check: Vehicle electrical fault repaired and circuit operation verified by instructor after repair. When performing diagnostic procedures the following items should always be followed: 1. Verify the complaint 2. Isolate the cause 3. Repair the fault 4. Recheck your repair
Module 14
Module 14
1
ECTC 0016C
Customer Concern:
Cause:
Corrective Action:
Figure 1
2
Module 14
1.
Record the following information here and on the repair order (Figure 1). Vehicle model: ______________________ Model year: ________________________
2.
Background information for Diagnosis #3: Customer Concern: ___________________________________ ___________________________________ ___________________________________ Repair History: ___________________________________ ___________________________________ ___________________________________
3.
With a teammate, think of all the possibilities for this incident. On the following page, list all of the possible causes for this condition. If you have difficulty recalling all of the possible causes, you may use any diagnostic resources within the classroom to help you build your list. Once your list is complete to your satisfaction, rank the causes in the order of most probable. In other words, number them in the order you would test them. Module 14
Module 14
3
Possible Causes (List all possible causes for the given symptoms)
ECTC 0016C
________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________
4
Module 14
4.
After completing step 3, discuss your strategy with the instructor.
5.
With the instructor’s approval, verify, isolate, repair and recheck the fault in the order you ranked them in step 3. Perform all tests necessary to verify each possible cause.
6.
During your diagnosis, list below the results of your findings for each of the items you check from the list you created. Item tested: Actual vehicle results: 1st _____________________________ 2nd _____________________________ 3rd _____________________________ Additional items tested: ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________
7.
Module 14
When you have repaired the problem on the vehicle and verified the repair, record the cause and corrective action on the repair order (page 2).
5
Module 14
As a result of this exercise, you should see the need for effective diagnostic skills and the benefit of taking your time to follow repair procedures and get the problem resolved before returning the vehicle to the customer.
ECTC 0016C
You have just completed this worksheet. You should now be able to verify, isolate, repair and recheck the fault in question. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials ______________________ Return the workstation to the condition that you found it.
6
Module 14
CIRCUIT DIAGNOSIS EXERCISE: #4
Objective:
Given a customer’s repair order, a service manual and a digital multimeter, verify, isolate, repair and recheck the fault in question.
Relevance: Circuit diagnosis is a critical part of making effective repairs. In this exercise you will be given a customer concern. The symptom applies to a vehicle which you must repair. You must verify, isolate, repair and recheck the cause of the malfunction using the customer repair order, vehicle service manual, appropriate test equipment, and all diagnosis skills. Resources: • Assigned vehicle • Electronic Service Manual • Digital Multimeter Skill Check: Vehicle electrical fault repaired and circuit operation verified by instructor after repair. When performing diagnostic procedures the following items should always be followed: 1. Verify the complaint 2. Isolate the cause 3. Repair the fault 4. Recheck your repair Module 15
Module 15
1
ECTC 0016C
Customer Concern:
Cause:
Corrective Action:
Figure 1
2
Module 15
1.
Record the following information here and on the repair order (Figure 1). Vehicle model: ______________________ Model year: ________________________
2.
Background information for Diagnosis #4: Customer Concern: ___________________________________ ___________________________________ ___________________________________ Repair History: ___________________________________ ___________________________________ ___________________________________
3.
With a teammate, think of all the possibilities for this incident. On the following page, list all of the possible causes for this condition. If you have difficulty recalling all of the possible causes, you may use any diagnostic resources within the classroom to help you build your list. Once your list is complete to your satisfaction, rank the causes in the order of most probable. In other words, number them in the order you would test them.
Module 15
Module 15
3
Possible Causes (List all possible causes for the given symptoms)
ECTC 0016C
________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________
4
Module 15
4.
After completing step 3, discuss your strategy with the instructor.
5.
With the instructor’s approval, verify, isolate, repair and recheck the fault in the order you ranked them in step 3. Perform all tests necessary to verify each possible cause.
6.
During your diagnosis, list below the results of your findings for each of the items you check from the list you created. Item tested: Actual vehicle results: 1st _____________________________ 2nd _____________________________ 3rd _____________________________ Additional items tested: __ _____________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________
7.
Module 15
When you have repaired the problem on the vehicle and verified the repair, record the cause and corrective action on the repair order (page 2).
5
Module 15
As a result of this exercise, you should see the need for effective diagnostic skills and the benefit of taking your time to follow repair procedures and get the problem resolved before returning the vehicle to the customer.
ECTC 0016C
You have just completed this worksheet. You should now be able to verify, isolate, repair and recheck the fault in question. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials ______________________ Return the workstation to the condition that you found it.
6
Module 15
CIRCUIT DIAGNOSIS EXERCISE: #5
Objective:
Given a customer’s repair order, a service manual and a digital multimeter, verify, isolate, repair and recheck the fault in question.
Relevance: Circuit diagnosis is a critical part of making effective repairs. In this exercise you will be given a customer concern. The symptom applies to a vehicle which you must repair. You must verify, isolate, repair and recheck the cause of the malfunction using the customer repair order, vehicle service manual, appropriate test equipment, and all diagnosis skills. Resources: • Assigned vehicle • Electronic Service Manual • Digital Multimeter Skill Check: Vehicle electrical fault repaired and circuit operation verified by instructor after repair. When performing diagnostic procedures the following items should always be followed: 1. Verify the complaint 2. Isolate the cause 3. Repair the fault 4. Recheck your repair Module 16
Module 16
1
ECTC 0016C
Customer Concern:
Cause:
Corrective Action:
Figure 1
2
Module 16
1.
Record the following information here and on the repair order (Figure 1). Vehicle model: ______________________ Model year: ________________________
2.
Background information for Diagnosis #4: Customer Concern: ___________________________________ ___________________________________ ___________________________________ Repair History: ___________________________________ ___________________________________ ___________________________________
3.
With a teammate, think of all the possibilities for this incident. On the following page, list all of the possible causes for this condition. If you have difficulty recalling all of the possible causes, you may use any diagnostic resources within the classroom to help you build your list. Once your list is complete to your satisfaction, rank the causes in the order of most probable. In other words, number them in the order you would test them.
Module 16
Module 16
3
Possible Causes (List all possible causes for the given symptoms)
ECTC 0016C
________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________
4
Module 16
4.
After completing step 3, discuss your strategy with the instructor.
5.
With the instructor’s approval, verify, isolate, repair and recheck the fault in the order you ranked them in step 3. Perform all tests necessary to verify each possible cause.
6.
During your diagnosis, list below the results of your findings for each of the items you check from the list you created. Item tested: Actual vehicle results: 1st _____________________________ 2nd _____________________________ 3rd _____________________________ Additional items tested: ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________
7.
Module 16
When you have repaired the problem on the vehicle and verified the repair, record the cause and corrective action on the repair order (page 2).
5
Module 16
As a result of this exercise, you should see the need for effective diagnostic skills and the benefit of taking your time to follow repair procedures and get the problem resolved before returning the vehicle to the customer.
ECTC 0016C
You have just completed this worksheet. You should now be able to verify, isolate, repair and recheck the fault in question. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials ______________________ Return the workstation to the condition that you found it.
6
Module 16
CIRCUIT DIAGNOSIS EXERCISE: #6
Objective:
Given a customer’s repair order, a service manual and a digital multimeter, verify, isolate, repair and recheck the fault in question.
Relevance: Circuit diagnosis is a critical part of making effective repairs. In this exercise you will be given a customer concern. The symptom applies to a vehicle which you must repair. You must verify, isolate, repair and recheck the cause of the malfunction using the customer repair order, vehicle service manual, appropriate test equipment, and all diagnosis skills. Resources: • Assigned vehicle • Electronic Service Manual • Digital Multimeter Skill Check: Vehicle electrical fault repaired and circuit operation verified by instructor after repair. When performing diagnostic procedures the following items should always be followed: 1. Verify the complaint 2. Isolate the cause 3. Repair the fault 4. Recheck your repair
Module 17
Module 17
1
ECTC 0016C
Customer Concern:
Cause:
Corrective Action:
Figure 1
2
Module 17
1.
Record the following information here and on the repair order (Figure 1). Vehicle model: ______________________ Model year: ________________________
2.
Background information for Diagnosis #6: Customer Concern: ___________________________________ ___________________________________ ___________________________________ Repair History: ___________________________________ ___________________________________ ___________________________________
3.
With a teammate, think of all the possibilities for this incident. On the following page, list all of the possible causes for this condition. If you have difficulty recalling all of the possible causes, you may use any diagnostic resources within the classroom to help you build your list. Once your list is complete to your satisfaction, rank the causes in the order of most probable. In other words, number them in the order you would test them.
Module 17
Module 17
3
Possible Causes (List all possible causes for the given symptoms)
ECTC 0016C
________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________ ________________________________________
4
Module 17
4.
After completing step 3, discuss your strategy with the instructor.
5.
With the instructor’s approval, verify, isolate, repair and recheck the fault in the order you ranked them in step 3. Perform all tests necessary to verify each possible cause.
6.
During your diagnosis, list below the results of your findings for each of the items you check from the list you created. Item tested: Actual vehicle results: 1st _____________________________ 2nd _____________________________ 3rd _____________________________ Additional items tested: ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________
7.
When you have repaired the problem on the vehicle and verified the repair, record the cause and corrective action on the repair order (page 2).
Module 17
Module 17
5
As a result of this exercise, you should see the need for effective diagnostic skills and the benefit of taking your time to follow repair procedures and get the problem resolved before returning the vehicle to the customer.
ECTC 0016C
You have just completed this worksheet. You should now be able to verify, isolate, repair and recheck the fault in question. If you have any doubt about your skills in completing this worksheet please return to step 1 and review your work. Once you are confident of your skills, have your instructor verify your work. Instructor’s Initials ______________________ Return the workstation to the condition that you found it.
6
Module 17
HOW T O USE A DIGIT AL MUL TIMETER TO DIGITAL MULTIMETER Module 18
Objective:
Given a digital multimeter, electrical components and a car, identify the different meter features, connect the test leads, and perform voltage, resistance, amperage and continuity tests.
Relevance: A digital multimeter is an important tool to diagnose electrical malfunctions. It can measure voltage, voltage drop, current, resistance and check continuity. A high impedance digital multimeter should be used to test automotive electrical circuits. Resources: • Digital Multimeter • Spark plug wire • AA battery • Paper clip • Assigned vehicle • Coolant temperature sensor • Fuel tank sending unit • Fuel injector • Wrapped harness • Good fuse • Faulty fuse • 1M relay with faulty coil circuit Skill Check: Prepare and connect a digital multimeter to measure voltage, resistance, amperage and continuity.
Module 18
1
Safety Information: ECTC 0016C
CAUTION: Never use the meter if the meter or test leads look damaged
Display
Bar Graph
Be sure the test leads and switch are in the correct position for the desired measurement. Never measure resistance in a circuit when power is applied. Never touch the probes to a voltage source when the test leads are plugged into the 10A or 300 mA input jack.
Test Selections
Rotary Switch Push Button (location may vary)
Never apply more than the rated voltage between any input jack and earth ground. Be careful when working with voltages above 60 VDC or 30 V AC. Such voltages VAC. pose a shock hazard. Keep your fingers behind the finger guards on the test probes when making measurements.
Input Jacks
WARNING: TO A VOID F ALSE READINGS, WHICH AVOID FALSE COULD LEAD T O POSSIBLE ELECTRICAL TO SHOCK OR PERSONAL INJUR Y, REPLACE INJURY THE BA TTER Y AS SOON AS THE BA TTER Y BATTER TTERY BATTER TTERY INDICA TOR INDICAT ( ) APPEARS.
Input Jacks
WARNING 10A RANGE UNFUSED. TO AVOID DAMAGE OR INJURY USE ONLY IN PROTECTED CIRCUITS WHICH CAN NOT EXCEED EITHER 20 AMPS OR 4000 VOLT-AMPS
POWER-ON OPTION: © AUTOMATIC TOUCH HOLD PRESS WHILE TURNING METER ON
Press and hold 2 sec. while turning meter ON
WARNING TO AVOID ELECTRICAL SHOCK REMOVE TEST LEADS BEFORE OPENING CASE. TO PREVENT FIRE INSTALL FUSES WITH AMP/VOLT RATINGS SHOWN. 630mA 250V FAST 3A 600V FAST – + NEDA 1604 9V 6F22 9V
2
Module 18
Digital Multimeter Display Symbols Symbol
Description
Module 18
Touch hold ON Negative polarity (switch meter leads when this is displayed) Bar graph of meter reading Over Limits (The reading is out of the range of the meter’s capability. Usually means OPEN circuit)
M
Mega (1 million)
k
kilo (1 thousand) Digital Multimeter Symbols Symbol
Description Alternating Current (AC)
V
Volts AC (VAC)
A
Amps AC Direct Current (DC)
V
Volts DC (VDC)
A
Amps, DC
Ω 300mV
Ohms (resistance) DC Volts less than 300mV Diode
))) )
Audible Continuity Important safety information Ground Meter fuse Double Insulation 9V battery
Module 18
3
A
Rotary Switch
ECTC 0016C
B
1. C
D E
F G
4
To switch the meter ON, rotate the meter switch (left illustration) from OFF to another setting. Each switch setting has only one function. Identify the switch functions by filling in the correct letter for each function: ____
Amps, AC
____
Ohms resistance
____
Volts, DC
____
Diode/Continuity
____
Volts, AC
____
Amps, DC
____
DC volts, 300 mV or less
Module 18
Input Jacks 2. 10A
B
C 1000V 750V
300 mA
A
FUSED
The meter has four (4) input jacks (left illustration). Both amperage jacks (A & B) are internally fused.
COM
WARNING:
D
NEVER ATTEMPT A VOLTAGE MEASUREMENT IF A TEST LEAD IS IN THE 10A JACK (B). YOU MIGHT BE INJURED OR DAMAGE THE METER. Identify the input jack which corresponds to the following switch positions: ____
Volts, Ohms, Diode Test and Continuity
____
Common (return) for Volts, Ohms, Diode Test and Continuity
____
Amps (10 A continuous)
____
Amps (less than 300 mA current)
Note: Red is the electrical color code for positive (+). Therefore, insert the red test lead into the C ). To measure current, use jack labeled V (C A ). the jack labeled 10A (A A ) to Only use the jack labeled “300mA” (A measure circuit current that is less than 300mA. Black is the electrical color code for negative (–). Insert the black test lead into the jack D ). labeled COM (D
Module 18
5
Module 18
ECTC 0016C
Display
Symbol Meaning AC DC V
k M m
Alternating current or voltage Direct current or voltage Volts Manual range or Touch Hold ON Ohms kilo, Units x 1,000 Mega, Units x 1,000,000 Milli, Units x 1/1000
3.
Readings appear on a liquid crystal display (LCD). See the figure below. The symbols on the display indicate meter status (see chart on left).
Digital segments
Low battery
Volts AC
Polarity incorrect
Volts DC
Touch Hold-ON or manual mode
Bar graph
M (Mega)/k (kilo)
ohms
Floating decimal locations
4.
The bar graph shows readings relative to the full scale range. The bar graph lengthens as the measurement value increases.
5.
When switched from OFF to any position, this bar graph display appears for 1 second as part of a self-test. The meter is now ready to take a measurement.
Note: If a measurement is too large to be displayed, the letters “OL” (over limit) are displayed. 6.
6
While the meter is in use, this symbol ( – + ) appears to show approximately 8 more hours of battery life.
Module 18
Using the Multimeter 7.
Verify both meter leads are connected to the input jacks (See the note on the bottom of page 5 if you are unsure).
8.
Rotate the meter switch to display resistance ( ). On the illustration at left, record the meter display. What does this measurement indicate? ____________________________________
9.
Now touch the leads together. Record the reading at left.
Note: If the meter reading displays very low resistance (
View more...
Comments
