Table of Contents

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C-30-108-000/MP-001 - First, Second and Third Line Maintenance Instructions — Part 5

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C-30-108-000/MP-001 - First, Second and Third Line Maintenance Instructions

C-30-108-000/MP-001
1991-06-10 Ch 2695 Pages
PDF (12,573 KB)

Canadian Department of National Defence logo
C-30-108-000/MP-001

First, Second and Third Line Maintenance Instructions — Part 5

Truck Utility, Light 4 x 4 Military Design Iltis Canadian Series
Issued on Authority of the Chief of the Defence Staff
OPI: DSVPM
1986-10-31
1991-06-10 Ch 2
Canada logo

   The following sections have been extracted from the original CFTO document. For ease of use, some hyperlinks, reformatting, and minor modifications may have been made. English only. Pour la version français, télécharger le document original.

   This article contains only Part 5 — Electrical System.

Due to the length of this document, each of its six parts have a dedicated page. Other parts are available here:

Table of Contents



WARNING — With the exception of the alternator and some minor components (e.g. composite taillight assemblies), all parts on the Iltis Canadian Series are dimensioned in the metric system. During any maintenance procedures, all replacement fasteners must have the same measurement and strength as those removed. (Numbers on the heads of metric bolts and on the surfaces of metric nuts indicate their strength). Mismatched or incorrect fasteners may result in personal injury or engine damage or malfunction. Therefore, fasteners removed from the engine should be saved for re-use in the same location where possible. When fasteners are unsatisfactory for re-use, care should be taken to select a replacement that matches the original.

Part 5 — Electrical System

Section 1 — General

General

Introduction

1.Part 5 consists of the following sections:

  1. General, Section 1;
  2. Component Removal and Installation, Section 2;
  3. Troubleshooting, Section 3.

2.The charging and starting systems are dealt with in Part 2, Section 5.

Description of Electrical System

3.The vehicle has a 24-volt, negative-ground, electrical system that consists of the following:

  1. Two 12-volt batteries connected in series that supply power to all circuits on the vehicle.
  2. A multipolar, series-wound starter (refer to Part 2, Section 5, for description of starter).
  3. A heavy duty alternator (refer to Part 2, Section 5, for description of alternator).
  4. A slave receptacle can be used with a slave cable to start the vehicle, if the batteries are dead, or can be used to start another SMP vehicle with dead batteries. The connections are offset to prevent incorrect polarity connection. A jumper cable should not be used if a slave cable is available.
  5. There is a trailer receptacle on the rear of the vehicle for an intervehicular cable. The receptacle is used to connect the electrical system of the vehicle with a trailer for the operation of the trailer service lights and blackout tail-lights. Trailer lights are controlled by the master light switch in conjunction with the vehicle lights. The receptacle cover is held closed by a spring when the receptacle is not in use.
  6. A battery master switch controls all current from the batteries to the vehicle with the exception of the starter, alternator, slave receptacle and radio power supply box.
  7. The master light switch controls all lights on the vehicle with the exception of the warning lights, which are controlled by individual sending units. The master light switch must be “ON” for the warning lights to operate.
  8. The radio power supply box receives battery voltage at all times and is a means to connect radios to the battery supply. The outlets provide 24 volts to operate radios.
Operation of Electrical System

4.When the accessory switch is moved to the “ON” position, current from the batteries flows to the ignition circuit and accessories circuit. With the accessory switch in either the “ON” or “OFF” position, current from the batteries flows to the alternator, starter, and fan thermoswitches. Caution must be taken when working around these components. The radio power supply box is on a separate circuit with the batteries and receives battery current at all times.

Description of Circuit Breakers

5.The electrical system is protected by six circuit breakers. The breaker panel is located on the rear of the switch panel. The breakers protect the following circuits:

  1. Horn;
  2. Radiator Fans (Left and Right);
  3. Wiper Motor;
  4. Blower Motor;
  5. Fuel Pump.

The radio outlet circuit is protected by a separate breaker located in the radio power supply box which is mounted on the inside of the rear panel.

Description of Lighting System

6.Power for the lighting system is provided by the battery or charging system, depending on battery charge and alternator charging rate. Turn signals are controlled by a switch on the steering column.

Description of Sending Units

7.Changes in temperature or pressure vary the electrical resistance of the sending units. These electrical changes are indicated by units of measurement on the gauges or by the illumination of warning lights. The sending units are mounted in the area being monitored.

Wiring Harnesses

8.The chassis wiring harnesses are made up of cables, connectors, plugs, receptacles and terminals needed to carry power to electrical components. They terminate in connector plugs, connector receptacles and/or cable terminals. A trailer electrical receptacle is provided. The harnesses are secured to the vehicle by plastic clips.

Section 2 — Component Removal and Installation

General

WARNING — Do not replace metric bolts with standard bolts. See WARNING page at the front of the manual.

General

1.Section 2 describes electrical circuit components, and their removal, inspection and installation.

WARNING — Due to their higher power capabilities, the following procedures must be observed before beginning any tests on a 24 volt system.

Do not permit a “hot” wire to touch metal parts of the vehicle at any time. “Flash” testing by striking a hot wire against a vehicle ground will cause an arc that will completely destroy the connector on the lead.

Accidental contact of metal tools between battery or starter cables and the frame of the vehicle will cause a direct short circuit. This will result in arcing and instant heating of the tools to red hot. This can cause painful burns to the hands and serious damage to tools, vehicle components and batteries. Moreover, the overloaded battery may explode, spraying hot acid and sharp fragments over the surrounding area.

WARNING — To prevent injury, ensure the battery ground cable terminal of the left battery is disconnected before removing or installing electrical components. When switched off, the battery master switch does not disconnect the alternator, starter, slave receptacle or radio power supply box.

Horn

2.Removal — To remove, proceed as follows:

  1. Check the horn as per the troubleshooting guide (refer to Section 3).
  2. Turn off the battery master switch.
  3. Disconnect the two terminal connectors from the horn.
  4. Remove the two cap screws securing the horn and bracket to the fender.
  5. Remove the horn and the mounting bracket.
  6. Remove the securing nut from the back of the horn and remove the horn from the bracket.

3.Installation — To install, proceed as follows:

  1. Install the horn to the mounting bracket.
  2. Install the horn and bracket to the fender with the two cap screws.
  3. Connect terminal connectors 25A and 91G to the horn.
  4. Turn on the battery master switch, and test the horn.
Oil Temperature Sending Unit

4.Removal — To remove, proceed as follows:

  1. Disconnect the electrical wire from the sending unit.
  2. Remove the sending unit from the oil filter housing.

5.Installation — To install, proceed as follows:

  1. Install a new copper washer on the sending unit and install the sending unit in the oil filter housing.
  2. Connect electrical wire #34 to the sending unit terminal.
  3. Test for operation.
Oil Pressure Sending Unit

6.Removal — To remove, proceed as follows:

  1. Disconnect the electrical wires from the sending unit.
  2. Remove the sending unit from the cylinder head.

7.Installation — To install, proceed as follows:

CAUTION — To prevent damage to the sending unit, do not overtighten during installation.

  1. Install a new copper washer on the sending unit and install the sending unit in the cylinder head and tighten.
  2. Connect electrical wires #35 and #36 to the sending unit terminals.
  3. Test for operation.
Coolant Temperature Sending Unit (Gauge)

8.Removal — To remove, proceed as follows:

WARNING — To prevent injury, allow the engine to cool before removing the cap from the expansion reservoir.

  1. Remove the cap from the expansion reservoir to relieve pressure in the cooling system.
  2. Disconnect the wire from the coolant temperature gauge sending unit.
  3. Remove the sending unit from the housing.

NOTE — A small amount of coolant will be lost when the sending unit is removed.

9.Installation — To install, proceed as follows:

  1. Install the sending unit into the sending unit housing.
  2. Connect electrical wire #33 to the sending unit terminal.
  3. Add coolant to the expansion reservoir until the coolant level is correct and install the expansion reservoir cap.
  4. Test for operation.
Coolant Temperature Warning Light Sending Unit

10.Removal — To remove, proceed as follows:

WARNING — To prevent injury, allow the engine to cool before removing the cap from the expansion reservoir.

  1. Remove the cap from the expansion reservoir to relieve the pressure in the cooling system.
  2. Disconnect the electrical wire from the warning light sending unit.
  3. Remove the sending unit from the housing.

NOTE — A small amount of coolant will be lost when the sending unit is removed.

11.Installation — To install, proceed as follows:

  1. Install the sending unit in the housing.
  2. Connect electrical wire #32 to the sending unit terminal.
  3. Add coolant to the expansion reservoir until the coolant level is correct and install the expansion reservoir cap.
  4. Test for operation.
Two-wheel Drive Sending Unit

12.General — The two-wheel drive sending unit consists of a microswitch which activates the two-wheel drive warning light when the differential of the transaxle is disengaged.

13.Removal — To remove, proceed as follows:

  1. Check the sending unit as per the troubleshooting guide (refer to Section 3).
  2. Disconnect the two wires from the sending unit.
  3. Remove the sending unit from the front differential housing.

14.Installation — To install the two-wheel drive sending unit, proceed as follows:

CAUTION — Do not overtighten the sending unit. It is made of aluminium and is easily damaged.

  1. Install a new unit in the differential housing.
  2. Connect wires #80 and #91F to the sending unit.
  3. Test for operation.
Rear Differental Lock Sending Unit

15.General — The rear differential lock sending unit consists of a switch mounted on the differential which is activated when the differential lock is engaged. A red warning light on the dash is lit when the differential is locked.

16.Removal — To remove, proceed as follows:

  1. Check the sending unit as per the troubleshooting guide (refer to Section 3).
  2. Disconnect the wires from the sending unit.
  3. Remove the sending unit from the rear differential housing.

17.Installation — To install, proceed as follows:

CAUTION — Do not overtighten the sending unit. It is made of aluminium and is easily damaged.

  1. Install a new unit in the differential housing.
  2. Connect wires #82 and #90D to the sending unit.
  3. Test for operation.
Brake Light Switch

18.Removal — To remove, proceed as follows:

  1. Turn off the battery master switch.
  2. Disconnect the electrical leads from the switch terminals.
  3. Remove the switch from the master cylinder.

19.Installation — To install, proceed as follows:

  1. Install the switch in the master cylinder.
  2. Connect electrical leads #75 and #75A to the switch terminals.
  3. Bleed the master cylinder.
  4. Turn on the battery master switch.
  5. Test for operation.
Hand Brake Warning Light Switch

20.Removal — To remove, proceed as follows:

  1. Check the switch as per the troubleshooting guide (refer to Section 3).
  2. Disconnect wires #90A and #22A from the switch.
  3. Remove the two screws.
  4. Remove the switch.

21.Installation — To install, proceed as follows:

  1. Install the switch, ensuring the switch lever goes under the brake cable yoke.
  2. Install the switch, using the two screws.
  3. Connect wire #90A to the rear terminal.
  4. Connect wire #22A to the front terminal.
  5. Test the hand brake warning light.
Battery Master Switch

22.Removal — To remove, proceed as follows:

  1. Check the switch as per the troubleshooting guide (refer to Section 3).
  2. Disconnect the battery ground cable.
  3. Remove the two Philips-head machine screws, lock washers and nuts from the switch.
  4. Remove the switch from the bracket. Remove the nuts and lock washers from the cable posts, and disconnect the cables.

23.Installation — To install, proceed as follows:

CAUTION — Ensure the cables are connected to the correct posts before connecting the battery ground cable. Consult the wiring diagram, see Figure 5-2-9, at the end of this section, if necessary.

  1. Install the cables to the posts with the lock washers and nuts.
  2. Install the battery, master switch into the bracket and secure with two Phillips-head machine screws, lock washers and nuts.
  3. Connect the battery ground cable.
  4. Test for operation.
Slave Receptacle

24.Removal — To remove, proceed as follows:

  1. Check the slave receptacle as per the troubleshooting guide (refer to Section 3).
  2. Disconnect the battery ground cable.
  3. Remove the four machine screws and lock washers that secure the receptacle to the mounting bracket.
  4. Remove the battery master switchfrom the mounting bracket.
  5. Disconnect the slave positive (+) cable #15 from the battery master switch.
  6. Disconnect the ground cable #50 from the body (left of the receptacle).
  7. Remove the positive cable from the securing clips at the rear of the dash, and along the right side of the vehicle.
  8. Disconnect the positive cable from the positive battery terminal.
  9. Remove the receptacle from the bracket and remove the cable from the vehicle.

25.Installation — To install, proceed as follows:

  1. Feed the long positive cable behind the dash and along the right side to the battery.
  2. Install the cable in the retaining clips.
  3. Install the positive cable #15 to the battery master switch.
  4. Install the battery master switch on the mounting bracket.
  5. Install the ground cable #50 and the two other ground cables to the body.
  6. Install the slave receptacle on its mounting bracket with four machine screws and lock washers.
  7. Connect the positive cable to the positive battery terminal.
  8. Connect the battery ground cable to the battery ground terminal.
  9. Test for operation.
Master Light Switch

26.Removal — To remove, proceed as follows:

  1. Check the light switch as per the troubleshooting guide (refer to Section 3).

Figure 5-2-1 — Master Light Switch Securing Screws
Figure 5-2-1 — Master Light Switch Securing ScrewsClick image to enlarge.

  1. Disconnect the battery ground cable.
  2. Remove the switch panel from the dash.
  3. Remove the harness locking collar from the rear of the switch and remove the harness connector from the light switch.
  4. Remove the three screws and lock washers that secure the three light switch levers and remove the levers.
  5. Remove the four securing screws from the master light switch, see Figure 5-2-1, and remove the switch from the panel.

27.Installation — To install, proceed as follows:

  1. Insert the master light switch through the rear of the switch panel.
  2. Install the four securing screws.
  3. Install the three light switch levers with screws and lock washers.
  4. Connect the harness connector to the rear of the switch ensuring the slot in the connector aligns with the lug on the bottom of the switch receptacle.
  5. Install the harness locking collar on the receptacle and tighten until it is fully home.
  6. Install the switch panel on the dash.
  7. Connect the battery ground cable.
  8. Test the switch to ensure it functions correctly.
Accessory Switch

28.General — The accessory switch controls the current to the light switch, gauges and indicators and to the starter button, horn switch, fuel pump, windshield wiper motor switch and heater blower motor switch as well as the ignition system.

29.Removal — To remove, proceed as follows:

  1. Check the switch as per the troubleshooting guide (refer to Section 3).
  2. Turn off the battery master switch.
  3. Remove the switch panel from the dash.
  4. Remove the lever from the switch assembly.
  5. Remove the nut, lock washer, and switch identification plate.
  6. Disconnect the four bayonet-type connectors from the switch.
  7. Remove the switch from the panel.

Figure 5-2-2 — Accessory Switch Connectors
Figure 5-2-2 — Accessory Switch ConnectorsClick image to enlarge.

30.Installation — To install, proceed as follows:

  1. Connect the four bayonet-type connectors to the switch, see Figure 5-2-2. Connect wire #11 at the top right (“A”), wire #27 at top left (“B”), wire #2A at bottom left (“D”) and wire #11 at bottom right (“C”).

NOTE — Both #11 wires splice into the same single wire.

  1. Install the accessory switch in the switch panel, ensuring the locating pin is engaged in the hole in the panel.
  2. Install the identification plate with “OFF” at the 12 o'clock position.
  3. Install the nut and lock washer.
  4. Install the accessory switch lever with the screw and lock washer, ensuring the flats in the lever align with the flats on the switch shaft.
  5. Turn on the battery master switch and test the accessory switch.
Turn Signal Lights and Hi-Lo Beam Control Lever and Windshield Wiper Control

Figure 5-2-3 — Turn Signal Lights and Hi-Low Beam Control Lever Securing Screws
Figure 5-2-3 — Turn Signal Lights and Hi-Low Beam Control Lever Securing ScrewsClick image to enlarge.

31.Removal — To remove, proceed as follows:

  1. Turn off the battery master switch.
  2. Remove the steering wheel (refer to Part 4, Section 1).
  3. Remove the lower and upper steering column covers and the inner dust cover.
  4. Disconnect the three electrical connectors from the control levers.
  5. Remove the three securing screws, see Figure 5-2-3, and remove the control levers.

32.Installation — To install, proceed as follows:

  1. Install the control levers with three screws.
  2. Connect the electrical connectors to the control levers.
  3. Install the upper and lower steering column covers and the inner dust cover.
  4. Install the steering wheel (refer to Part 4, Section 1).
  5. Turn on the battery master switch.
  6. Test for operation.
Starter Button

33.Removal — To remove, proceed as follows:

  1. Turn off the battery master switch.
  2. Remove the switch panel from the dash.
  3. Loosen the inner dust cover clamp at the top of the steering column covers.
  4. Remove the two screws from the lower steering column cover and remove the lower cover.
  5. Disconnect the starter button electrical connector.
  6. Remove the locking nut and washer from the starter button.
  7. Disconnect the turn signal/horn multiple connector.
  8. Remove the starter button from the bracket and dash.

34.Installation — To install, proceed as follows:

  1. Connect the starter button electrical connector.
  2. Turn on the battery master switch and accessory switch and test the start button.
  3. Turn off the battery master switch.
  4. Disconnect the wires and install the starter button wires through the dash and over the steering column.
  5. Connect the electrical connectors.
  6. Insert the button into the bracket and install the lock washer and nut. Do not overtighten.
  7. Connect the signal/horn multiple connector.
  8. Install the lower steering column cover.
  9. Tighten the inner dust cover clamp.
  10. Install the switch panel to the dash.
  11. Turn on the battery master switch.
Heater/Hazard Switch Assembly

35.General — The heater control and hazard light switches share the same receptacle. The receptacle is secured to the dash by two spring clips.

36.Removal — To remove, proceed as follows:

  1. Check the switches as per the troubleshooting guide (refer to Section 3).
  2. Turn off the battery master switch.
  3. Remove the gauge panel.
  4. Pry the heater/hazard light switch assembly from the dash.
  5. Remove the red multiple connector from the top of the hazard light switch and the single connector from the bottom.
  6. Remove the white and red multiple connector from the bottom of the heater switch and the two single black connectors from the top.

37.Installation — To install, see Figure 5-2-4 and proceed as follows:

Figure 5-2-4 — Heater/Hazard Switch Connectors
Figure 5-2-4 — Heater/Hazard Switch ConnectorsClick image to enlarge.

  1. Connect the white and red multiple connector to the bottom of the heater switch and the two single black connectors to the top. The heater switch is at the left side of the assembly.
  2. Connect the single wire to the connector at the bottom of the hazard light switch.
  3. Connect the red multiple connector to the top of the 'hazard light switch.
  4. Install the heater/hazard switch assembly in the dash. Push in the assembly until the retaining clips engage.
  5. Turn on the battery master switch.
  6. Test the operation of the heater and hazard lights.
Gauge Panel

38.General — The gauge panel supports the oil pressure gauge, the coolant temperature gauge and the battery/alternator indicator gauge. The panel is secured to the dash by four quick disconnect fasteners.

39.Removal — To remove, proceed as follows:

  1. Turn off the battery master switch.
  2. Unfasten the four one-quarter-turn panel fasteners, and pull the gauge panel from the dash.

40.Installation — To install, proceed as follows:

  1. With the gauges installed, position the panel in the dash.
  2. Secure the gauge panel to the dash with the four one-quarter-turn fasteners.
  3. Turn on the battery master switch.

NOTE — To remove the individual gauges, follow the procedures described below for each gauge.

Oil Pressure Gauge

41.Removal — To remove, proceed as follows:

  1. Check the gauge as per the troubleshooting guide (refer to Section 3).
  2. Remove the gauge panel.
  3. Disconnect the multiple connector from the bottom of the gauge.
  4. Remove the light and light holder from the rear of the gauge.
  5. Remove the two knurled securing nuts and the securing bracket.
  6. Remove the gauge through the panel front.

42.Installation — To install, proceed as follows:

  1. Insert the back of the gauge through the front of the panel.
  2. Position the securing bracket over the two mounting screws.
  3. Install the two knurled nuts on the mounting screws.
  4. Connect the multiple connector to the bottom of the gauge.
  5. Install the light holder and light.
  6. Install the gauge panel.
Coolant Temperature Gauge

43.Check the gauge as per the troubleshooting guide (refer to Section 3). For removal and installation, follow the same procedures for the oil pressure gauge.

Battery/Alternator Indicator

44.Check the gauge as per the troubleshooting guide (refer to Section 3). For removal and installation, follow the same procedures for the oil pressure gauge.

Warning Lights

45.General — The hand brake, rear differential lock and two-wheel drive warning lights are located on the dash above the gauge panel. Access to the rear of the lights is through the gauge panel opening. The removal and installation procedure is the same for all three warning lights.

46.Removal — To remove, proceed as follows:

  1. Check the warning light as per the troubleshooting guide (refer to Section 3).
  2. Remove the gauge panel.
  3. Remove the bulb holder from the dash.
  4. Remove the bulb.

47.Installation — To install, proceed as follows:

  1. Install a new bulb in the holder.
  2. Install the bulb and holder in the dash.
  3. Install the gauge panel.
Radio Receptacle Power Supply Box

48.Removal — To remove, proceed as follows:

  1. Check the power supply box as per the troubleshooting guide (refer to Section 3).
  2. Disconnect the battery ground cable.
  3. Disconnect and remove the radios.
  4. Remove the six self-locking nuts from the power supply box.
  5. Remove the box from the rear panel and turn it around for easy access.
  6. Disconnect the positive and negative wires.
  7. Remove the supply box from the vehicle.

49.Installation — To install, proceed as follows:

  1. Connect the positive wire to the positive terminal and negative wire to the negative terminal in the supply box.
  2. Install the supply box to the inside of the rear panel with the six self-locking nuts.
  3. Connect the battery ground cable.
Trailer Receptacle

50.Removal — To remove, proceed as follows:

  1. Check the receptacle as per the troubleshooting guide (refer to Section 3).
  2. Turn off the battery master switch.
  3. Remove the four cap screws that secure the receptacle door to the housing.
  4. Remove the four cap screws that secure the mounting bracket to the vehicle body.
  5. Remove the harness locking collar from the back of the trailer receptacle.
  6. Remove the grommet and slide it onto the wires, out of the way.
  7. Using needle nosed pliers, remove the terminals from the receptacle and tag the wires for reinstallation.

51.Installation — To install, proceed as follows:

  1. Match up and insert tagged terminals into the receptacle, see Figure 5-3-11.
  2. Slide the grommet down the wires and insert it into the receptacle.
  3. Install the harness locking collar on the rear of the receptacle.
  4. Install the mounting bracket to the vehicle body with the four cap screws.
  5. Install the receptacle door on the housing so that the door swings upwards.
  6. Turn on the battery master switch.
Wiring and Harnesses

52.General — The different circuits can be identified by reference to the wiring diagrams. All terminals are identified with circuit numbers, see Figure 5-2-5, Figure 5-2-6 and Figure 5-2-7. For the electrical system schematic, see Figure 5-2-9.

Figure 5-2-5 — Front Wiring Harness

Legend
No 		Component Wire
No 		Wire Connection Point
1. Right front harness connector under dash, right side 37B 1 - Starter.
20 2 - Blackout Marker.
491 3 - Park Light.
91D 4 - Park Light.
18 5 - Headlight — Low Beam.
17 6 - Headlight — Low Beam.
460 7 - Right Turn Signal
1C 8 - Fuel Cutoff Valve.
74A 9 - Starter.
2. Ballast resistor under hood, left side 37A Resistor Interconnecting Wire.
37B Resistor to Starter.
37 Resistor to Coil Suppressor.
27B Resistor from Accessory Switch.
3. Ignition circuit connector under dash, left side 1 1 - D+ Alternator.
27A 2 - Transistorized Ignition Unit.
37B 3 - Ballast Resistor.
4. Sending unit connector under dash, left side 80 1 - Two-Wheel Drive Switch.
33 2 - Coolant Temperature Sensor.
36 3 - Oil Pressure Sensor.
22B 4 - Brake Fluid Level Switch.
35 5 - Oil Pressure Switch.
51 6 - Windshield Washer Motor.
34 7 - Oil Temperature Switch.
5. Left front harness connector under dash, left side 18 1 - Headlight.
17 2 - Headlight.
461 3 - Signal Light.
20 4 - Blackout Marker.
491 5 - Park Light.
19 6 - Blackout Drive Light.
75 7 - Brake Light Switch.
75A 8 - Brake Light Switch.
25A 9 - Horn.
6. Fan circuit breakers under dash, left side 84 Left Fan.
85 Right Fan.
7. Battery master switch 1D To Alternator Regulator terminal.
8. Ground point — Left cab floor 52 Alternator Ground Point.
9. Ground point — Left fender wall 91D Engine Ground.
95
10. TCI unit socket — Firewall 27A A - From Accessory Switch.
95 B - Ground.
11. Windshield washer motor — Left fender wall 51 From Wiper Control.
91K Ground.
12. Coil suppressor — Left fender wall 37 From Ballast Resistors.
13. Brake light switch — Under master cylinder 75 To Master Light Switch.
75A To Master Light Switch.
14. Brake fluid level switches — Tops of brake fluid reservoirs 22C Front to Rear Reservoir.
91J Front to Rear Reservoir.
22B To Brake Warning Light.
91H Ground.
15. Two-wheel drive switch — Right side transaxle 80 To Warning Light.
91F Ground.
16. Coolant temperature switch — Coolant temperature sensor 32 To Coolant Temperature Light.
33 To Coolant Temperature Gauge.
17. Oil pressure switch — Oil pressure sensor 35 To Oil Pressure Light.
36 To Oil Pressure Gauge.
18. Oil temperature switch — On oil filter base 34 To Oil Temperature Light.
19. Alternator 1 D+ to Cutout Relay.
1D To Battery Master Switch.
2 B+ to Starter.
52 Ground.
20. Horn 25A To Horn Relay.
91G Ground.
21. Starter 2 To Alternator.
6 From Slave Receptacle.
37B From Ballast Resistors.
74A From Starter Button.
22. Air/Fuel cutoff valve 1C From Accessory Switch.
23. Ground Point — Right fender wall 91 Right Head Light.
91C Right Blackout Marker.
91D Right Harness Ground.
91B Right Turn Signal Light.
91A Right Parking Light.
24. Right front turn signal 91B Ground 22 Right Fender.
460 Brake and Signal Flasher Unit.
25. Right headlight 17 High Beam from Dimmer Switch.
18 Low Beam from Dimmer Switch.
91 Ground 22 Right Fender.
26. Right park light 91A Ground 22 Right Fender.
491 From Master Light Switch.
27. Right blackout marker 20 From 24 at Master Light Switch.
91C Ground 22 Right Fender.
28. Right cooling fan 85A From Bottom Thermoswitch.
96C Ground to Fan Bracket.
96B Ground to 31 Left Fender.
29. Left cooling fan 84A From Top Thermoswitch.
96A Ground to Fan Bracket.
96 Ground to 31 Left Fender.
30. Left fan thermoswitch 84 From Circuit Breaker.
84A To Left Fan Motor.
31. Right fan thermoswitch 85 From Circuit Breaker.
85A To Right Fan Motor.
32. Ground point — Left fender wall 91 Left Headlight.
91A Left Park Light.
91C Left Blackout Marker.
91D Left Harness Ground.
91E Left Blackout Drive Light.
96 Left Cooling Fan.
96B Right Cooling Fan.
91B Left Turn Signal Ground.
33. Left park light 491 From Master Switch.
91A Ground to 31 Left Fender.
34. Left headlight 17 High Beam from Dimmer Switch.
18 Low Beam from Dimmer Switch.
91 Ground to 31 Left Fender.
35. Left signal light — Front body 461 From Brake and Signal Flasher.
91B Ground.
36. Blackout drive light 19 From Master Light Switch.
91E Ground to 31 Left Fender.
37. Left blackout marker 20 From Master Light Switch.
91C Ground to 31 Left Fender.

Figure 5-2-5 — Front Wiring HarnessClick image to enlarge.


Figure 5-2-6 — Dash Wiring Harness

Legend
No 		Component Wire
No 		Wire Connection Point
1. Speedometer head (see also figure 5-2-8 460A Turn Signal Warning Light To Signal Flasher Unit.
461A Turn Signal Warning Light To Signal Flasher Unit.
467B Trailer Signal Warning Light To Signal Flasher Unit.
35 Oil Pressure Light to Oil Pressure Switch.
93E Ground to Speedo Head Lug.
17 High Beam Indicator Light To Dimmer Switch.
28 Fuel Gauge from Sending Unit.
27F Fuel Gauge from Accessory Switch.
81F Oil Temp. Light from 81E.
81E Coolant Temperature Light from 81D.
81D Oil Pressure and Alternator Light from Warning Light Relay.
34A Alternator Light to Diode.
1B Alternator Light to Alternator D+ Relay.
32B Coolant Light.
32 Coolant Temperature Light to Coolant Temperature Switch.
34B Oil temperature Light to Diode.
34 Oil Temperature Light to Oil Temperature Switch.
40 Left Hand Dash Lights.
40A Right Hand Dash Lights.
2. Turn signal and horn button switch 60 To brake and Signal Flasher.
463 To Emergency Flasher Switch 49A.
61 To Brake and Signal Flasher.
25B To Horn Relay 85.
3. Windshield wiper control 51 Wiper Switch to Wiper Motor.
53 Wiper Switch to Wiper Motor 53.
53A Wiper Switch to Wiper Motor 53A.
53B Wiper Switch to Wiper Motor 53B.
53E Wiper Switch to Wiper Motor 53E.
4. Dimmer switch 16 To Master Light Switch.
16A To Splice at #460/461.
17 To High Beam Indicator Light.
18 To Headlights.
5. Relays under Dash — Left to right horn relay 25B To Horn Button.
25A To Horn.
25 To Horn Circuit Breaker.
25 Interconnecting Wire to 25 Horn Circuit Breaker.
Alternator D+ cutout relay 1A From Warning Light Relay.
1 To Alternator D+.
1B To Alternator Warning Light.
93H To Ground Point 11.
93K To Warning Light Relay.
Relay warning light relay 2A From Accessory Switch.
2B From Splice at 460/461 at Master Light Switch.
1A To Cutout Relay Alternator D+.
81D To Feed Alternator and Oil Pressure Lights.
93K From Cutout Relay.
6. Circuit breakers from left to right
1. Fuel pump
2. Left hand coolant fan
3. Right hand coolant fan
4. Horn
5. Windshield wiper motor
6. Heater blower motor 		83A To Fuel Pump Circuit Breaker.
12 To Left Hand Fan Circuit Breaker.
12A To Right Hand Fan Circuit Breaker.
25 From Horn Circuit Breaker.
10 To Horn Circuit Breaker.
50 From Wiper Circuit Breaker.
50A To Wiper Circuit Breaker.
13 From Heater Blower Circuit Breaker.
13A To Heater Blower Circuit Breaker.
7. Battery master switch 1D To Alternator Regulator Terminal.
15 To Splice for Accessory Switch and Terminal “F” of Master Light Switch.
15 From Slave Receptacle.
8. Connector to rear harness 82 1 - To Differential Lock Switch.
22A 2 - To Hand Brake Switch.
28 3 - To Fuel Level Sending Unit.
23 4 - To Blackout Stop Lights.
21 5 - To Service Tail-lights.
24 6 - To Blackout Tail-lights.
9. Ground point 91D Dash Harness Ground.
94 Wiper Motor Ground.
10. Ground point 93E Ground for Dashlights, Trailer Signal Warning Light, High Beam Indicator Light.
93 Ground for Alternator D + Cutout Relay, Brake/Turn Signal Flasher Unit, Emergency Flasher Switch and Light, Blower Motor and Switch, Battery Generator Indicator, Coolant Temperature Gauge, Oil Pressure Gauge, Map Reading Light, Battery Generator Indicator Light, Coolant Temperature and Oil Pressure Gauge Lights.
11. Brake/Turn signal flasher unit 460 To Right Front Signal Light.
461 To Left Front Signal Light.
12. Brake/Turn signal flasher unit 93 1 - To Ground Point 10.
60 2 - To Turn Signal Switch.
61 3 - To Turn Signal Switch.
467B 4 - Trailer Turn Signal Warning Light.
467 5 - To Turn Signal Switch.
2C 6 - To Splice at Wire 460/461 at Master Light Switch.
22 7 - To Master Light Switch.
13. Master light switch 75 A - Stop Light Feed.
40 B - Instrument Panel Feed.
22 C - Service Stop Light.
19 D - Blackout Drive Light.
24 E - Blackout Marker and Tail-lights.
15 F - Light Switch Feed from Master Switch.
21 H - Service Tail-light.
460/461 J - Front Turn Signals.
75A K - From Stop Light Switch.
491 L - Parking Lights.
16 M - Dimmer Switch Feed.
23 N - Blackout Stop Light.
14. Accessory switch 11 A - From Splice at Wire 15.
11 C - Battery Master Switch.
27 B - Feed to All Circuits.
2A D - Feed to Circuit Breakers and Relays.
15. Left front light connector 18 1 - To Headlight Low Beam.
17 2 - To Headlight High Beam.
461 3 - Turn Signal Light.
20 4 - To Blackout Marker.
491 5 - To Parking Light.
19 6 - Blackout Drive Light.
75 7 - Stop Switch Feed.
75A 8 - From Stop Light Switch.
25A 9 - To Horn.
32 10 - To Coolant Temperature Light.
16. Sending unit connector 80 1 - Two Wheel Drive Light.
33 2 - From Coolant Temperature Gauge.
36 3 - From Coolant Temperature Gauge.
22B 4 - From Brake Warning Light.
35 5 - From Oil Pressure Light.
51 6 - From Washer Switch.
34 7 - From Oil Temperature Light.
17. Starting circuit connector 1 1 - To Alternator D+ Relay.
27A 2 - From Accessory Switch to Ballast Resistor.
37B 3 - From Ballast Resistor to Starter.
18. Wiper motor connector 53A 1 - From Wiper Switch 53A.
53E 2 - From Wiper Switch 53E.
53 3 - From Wiper Switch 53.
53B 4 - From Wiper Switch 53B.
94 5 - From Ground Point 9.
19. Starter button connector 74 1 - From Accessory Switch Splice.
74A 2 - To Starter Solenoid 50.
20. Heater blower switch connector 13 1 - To Blower Motor Circuit Breaker.
13B 2 - Blower Switch Connector to Blower Motor.
29 3 - To Blower Motor.
29A 4 - To Blower Motor.
21. Heater blower motor connector 29 1 - From Blower Motor Switch.
29A 2 - From Blower Motor Switch.
93B 3 - To Ground.
22. Emergency flashing connector 460/461 To Light Switch 49.
460B To Turn Signal Light 49A.
467 To Turn Signal 30.
463 To Turn Signal Switch 15A.
23. Emergency flasher ground 93A Ground to Ground Point 10.
24. Oil pressure gauge light 40B From Splice at Dash Light Wire 40.
40C To Coolant Temperature Gauge Light.
25. Oil pressure gauge 27D To Coolant Temperature Gauge.
27C From Wire #27 Ignition.
36 To Oil Pressure Sensor.
93C Ground to Ground Point 10.
93D To Coolant Temperature Gauge.
26. Brake warning light 22B To Brake Fluid Level Switch 22B.
81 From Warning Light Relay.
81A To Differential Lock Light.
27. Coolant temperature gauge light 40C From Oil Pressure Gauge Light.
40D To Battery Generator Indicator Light.
28. Coolant temperature gauge 27E To Battery Generator Indicator.
27D From Oil Pressure Gauge.
33 To Coolant Temperature Sensor.
93D From Oil Pressure Gauge.
93E To Battery Generator Indicator.
29. Differential lock warning light 81A From Brake Warning Light.
81B To Two Wheel Drive Warning Light.
82 To Differential Lock Switch.
30. Battery generator indicator light 40D To Indicator Light.
31. Battery generator indicator 27E From Coolant Temperature Gauge.
93E To Coolant Temperature Gauge.
32. Two-wheel drive warning light 80 To Light Switch.
81B From Differential Lock Warning Light.
33. Map reading light 81C From Splice at 460/461 at Emergency Flasher Switch.
93C Ground to Ground Point 10.
34. Right front harness 37B 1 - Starter 15A to Resistors.
20 2 - To Blackout Marker.
491 3 - To Parking Light.
91D 4 - Ground to Ground Point 9.
18 5 - Headlight Low Beam.
17 6 - Headlight High Beam.
460 7 - Turn Signal.
1C 8 - Air/Fuel Cutoff Valve.
74A 9 - From Starter Button.

Figure 5-2-6 — Dash Wiring HarnessClick image to enlarge.


Figure 5-2-7 — Rear Wiring Harness

Legend
No 		Component Wire
No 		Wire Connection Point
1. Right rear composite light 90 Ground.
21 Right Tail-light.
22-460 Right Stop and Signal.
24 Right Blackout Marker.
23 Right Blackout Stop.
2. Trailer recepticle 490 H - Blackout Markers.
22-460 J - Right Stop and Signal.
22-461 B - Left Stop and Signal.
24 A - Blackout Markers.
24 C - Blackout Markers.
21 E - Tail-lights.
23 F - Blackout Stop.
90 D - Ground.
3. Left rear Composite light 90 Ground.
23 Left Blackout Stop.
24 Left Blackout Marker.
22-461 Left Stop and Signal.
21 Left Tail-light.
4. Licence plate light 90B Ground.
26 Licence Plate Light.
5. Ground 90F Ground.
6. Fuel level transmitter 90E Ground.
28 Fuel Level Gauge.
7. Differential lock switch 90D Ground.
82 Differential Lock Warning Light.
8. Fuel pump 90C Ground.
83 Fuel Pump Circuit Breaker.
9. Hand brake warning light switch 90A Ground.
22A Brake Warning Light.
10. Brake and turn signal unit — under dash 22-460 1 - Right Stop and Signal.
22-461 2 - Left Stop and Signal.
3 - Blank.
11. Under dash 83 Fuel Pump Circuit Breaker.
12. Under dash 90 Ground.
13. Rear harness connector under dash 82 1 - Differential Lock Switch.
22A 2 - Hand Brake Switch.
28 3 - Fuel Level Transmitter.
23 4 - Blackout Stop Lights.
21 5 - Tail-lights.
24 6 - Blackout Markers.

Figure 5-2-7 — Rear Wiring HarnessClick image to enlarge.


Figure 5-2-8 — Speedometer Head Electrical Terminals

Item
No 		Wire
No 		Circuit
1. 28 Fuel gauge sending unit.
2. 27F Fuel gauge accessory switch.
3. 40/40A Speedometer light.
4. 34/34B and 81F Oil temperature warning light.
5. 32/32B and 81E/81F Coolant temperature warning light.
6. 34A/1B Alternator warning light.
7. 460A Turn signal indicator light (right turn).
8. 81D/81E Alternator light and oil pressure light.
9. 461A Turn signal indicator light (left turn).
10. 35 Oil pressure warning light.
11. 467B Trailer turn signal indicator light.
12. 17 High beam indicator light.
13. 40A Speedometer light.
14. 93E Ground.

Figure 5-2-8 — Speedometer Head Electrical TerminalsClick image to enlarge.

Figure 5-2-9 — Electrical System Schematic

Sym Nomenclature
⊛ 3 Radio Power Supply Box
⊛ 2 Brake/Turn Signal Flasher Unit
⊛ 1 TCI Unit
Z1 Ignition Supressor
W1 Distributor
S21 Differential Lock Switch
S20 Starter Button
S19 Wiper Motor Switch
S18 Hand Brake Warning Light Switch
S17 Battery Master Switch
S16 Master Light Switch
S15 Accessory Switch
S14 Hi-Lo Beam Switch
S13 Horn Button Switch
S12 Turn Signal Switch
S11 Emergency Flasher Switch
S10 Blower Switch
S9 Brake Light Switch
S8 Brake Fluid Level Switch
S7 Brake Fluid Level Switch
S6 Oil Temperature Sending Unit
S5 Oil Pressure Sending Unit
S4 Coolant Temperature Sending Unit
S3 Two-Wheel Drive Light Switch
S2 Fan Thermo Switch
S1 Fan Thermo Switch
RT2 Oil Pressure Sending Unit
RT1 Coolant Temperature Sending Unit
R3 Fuel Level Sending Unit
R2 Ballast Resistor
R1 Ballast Resistor
P10 Male Connector
P9 Male Connector
P8 Male Connector
P7 Male Connector
P6 Male Connector
P5 Male Connector
P4 Male Connector
P3 Male Connector
P2 Male Connector
P1 Male Connector
M4 Gasoline Gauge
M3 Oil Pressure Gauge
M2 Coolant Temperature Gauge
M1 Battery/Alternator Indicator
LS1 Horn
L2 Ignition Coil
L1 Air/Fuel By-Pass Valve
K3 Relay - Warning Lights
K2 Relay - Cut-Out Alternator D+
K1 Relay - Horn
J12 Slave Receptacle
J11 Female Connector
J10 Female Connector
J9 Female Connector
J8 Female Connector
J7 Female Connector
J6 Female Connector
J5 Female Connector
J4 Female Connector
J3 Female Connector
J2 Female Connector
J1 Female Connector
G1 Alternator
E4 Spark Plug
E3 Spark Plug
E2 Spark Plug
E1 Spark Plug
D,CR3 Diode
D,CR2 Diode
D,CR1 Diode
DS35 Indicator Light for Hazard Warning Light
DS34 License Plate Light
DS33 LH Parking Light
DS32 LH Stop & Turn Signal
DS31 LH Blackout Maker Light
DS30 LH Blackout Stop Light
DS29 LH Blackout Stop Light
DS28 RH Blackout Marker Light
DS27 RH Stop & Turn Signal
DS26 RH Parking Light
DS25 High Beam Indicator Light
DS24 Turn Signal Warning Light (Trailer)
DS23 Dash Light
DS22 Dash Light
DS21 Turn Signal Indicator Light
DS20 Coolant Temperature Warning Light
DS19 Oil Temperature Warning Light
DS18 Alternator Warning Light
DS17 Oil Pressure Warning Light
DS16 Oil Pressure Gauge Light
DS15 Coolant Temperature Gauge Light
DS14 Battery/Alternator Gauge Light
DS13 Brake Warning Light
DS12 Differential Lock Warning Light
DS11 Two-Wheel Drive Light
DS10 Map Reading Light
DS9 LH Front Turn Light
DS8 LH Head Light
DS7 LH Parking Light
DS6 LH Blackout Marker Light
DS5 LH Blackout Drive Light
DS4 RH Blackout Marker Light
DS3 RH Head Light
DS2 RH Parking Light
DS1 RH Front Turn Light
CB7 Circuit Breaker - Radio Box
CB6 Circuit Breaker - Heater Fan
CB5 Circuit Breaker - Wiper
CB4 Circuit Breaker - Horn
CB3 Circuit Breaker - RH Radiator Fan
CB2 Circuit Breaker - LH Radiator Fan
CB1 Circuit Breaker - Fuel Pump
BT2 Battery
BT1 Battery
B7 Fuel Pump
B6 Wiper Motor
B5 Blower Motor
B4 Windshield Washer Pump
B3 Starter Motor
B2 RH Fan Motor
B1 LH Fan Motor

Figure 5-2-9 — Electrical System SchematicClick image to enlarge.

Section 3 — Troubleshooting

General

1.The tests and inspections are illustrated and presented step by step. They must be done in the order shown. These procedures suggest corrective action to take when a faulty component is found.

2.Wiring diagrams for the truck electrical system are used to supplement the tests and inspections. See Figure 5-2-5, Figure 5-2-6, Figure 5-2-7 and Figure 5-2-9.

3.When troubleshooting the lighting system, always look for dirty or corroded lamp sockets and connectors. Also look for pins which have been bent, broken or pushed back in their connectors. Clean, straighten or tighten connectors or lamp sockets, as needed, before replacing light bulbs or other parts.

Multimeter and Ohms Scale

4.When using the multimeter on the ohms scale, disconnect the battery ground cable terminal from the negative post of the left battery and disconnect the circuit being tested. The ohms scale is used for making tests for continuity, shorts and resistance. Proceed as follows:

CAUTION — Failure to disconnect the battery ground cables can result in damage to the multimeter. The battery master switch does not disconnect all vehicle circuits when switched off.

  1. The multimeter must be set-up and “zeroed” before making any tests.

NOTE — If the needle will note “zero” replace multimeter batteries. If the needle still will not “zero” after replacing batteries, replace the test leads or the meter.

  1. Voltage Scales — If the voltage range is not known, select a range higher than required and move the selector to the next lower scale until a reading is obtained.
  2. The red test probe must always be connected to the most positive side of the circuit.

General Notes

5.When connecting a meter probe to ground, make sure the ground point picked is a clean, unpainted area of the engine or body.

Electrical System Troubleshooting

6.Figure 5-3-1, Figure 5-3-2, Figure 5-3-3, Figure 5-3-4, Figure 5-3-5, Figure 5-3-6, Figure 5-3-7, Figure 5-3-8, Figure 5-3-9, Figure 5-3-10, and Figure 5-3-11, are tabulations of procedures for tests and inspections, with corrective actions for overcoming malfunctions in the electrical system. Calibration of meters used is covered in preceding paragraph 4.

Figure 5-3-1 — Steering System Troubleshooting

1. One or both headlights will not light. (All other lights are working.)

Test 1:
Disconnect the socket from the headlight bulb. Turn light switch to “SERVICE DRIVE”. Connect the positive probe to either wire #17 or #18.

  1. If the meter reads battery voltage (23-25 volts), replace the headlight bulb.
  2. If the meter shows no reading (0 volts), check the other wire or lift up on the dimmer switch lever once.
  3. If the meter now reads battery voltage, replace the headlight bulb.
  4. If the meter still shows no reading, do Test 2.

Test 2:
Remove the cover from the steering column. Disconnect the socket with the four wires from under the directional signal lever. Touch the positive probe to socket terminal #16. Reinstall the socket.

  1. If the meter reads battery voltage, the dimmer switch is N/S and must be replaced.
  2. If there is no voltage indicated, check the master light switch, do Test 3.

Test 3:
Remove the switch panel from the dash. Remove the connector from the light switch. Connect a jumper wire between terminal “F” and terminal “M” of the wire connector (see Figure 5-3-2).

  1. If the headlights now operate, replace the master light switch.
  2. If the lights still do not come on, repair or replace wire #16 between the connector and the dimmer switch.

2. Blackout drive, front blackout markers, park light or front turn signal will not light.

Test 1:
Disconnect the wire from the back of the light that is not working. Turn the light switch (and turn signal lever if necessary) to the position which matches the light being tested. Connect the positive probe to the disconnected wire.

  1. If meter reads battery voltage, replace the bulb (meter will fluctuate between 0 and battery voltage, if testing signal lights).
  2. If meter shows no reading (0 volts) when checking the turn signals, do Test 2 malfunction item 4.
  3. If the meter shows no reading (0 volts) when testing lights other than the signal lights, do Test 2.

Test 2:
Remove the switch panel from the dash. Remove the connector from the light switch. Connect a jumper wire from socket “F” to the socket of the light that is not working. (Also depress the brake pedal or move the turn signal control lever if checking those lights).

  1. Repair or replace the wiring between the light switch and either right or left connector.

3. Rear lights will not operate.

Test 1:
Disconnect the wire from the back of the light that is not working.

Wire no. Circuit
21 Service Taillights.
22-460 Service Stop and Turn Signal light - right.
22-461 Service Stop and Turn Signal light - left.
23 Blackout Stop-light.
24 Blackout Marker.
26 Licence Plate Marker.

Connect the positive probe to the wire. Turn the light switch, and the turn signal lever if necessary, to the position that matches the light being tested. Also depress the brake pedal, if checking service or blackout brake lights.

  1. If the meter reads battery voltage, replace the bulb. (Meter fluctuates between 0 volts and battery voltage if checking signal lights).
  2. If meter shows no reading (0 volts), do Test 2.

Test 2:
Remove the light panel from the dash. If checking the stop-light or turn signals, disconnect the two wire plug with wires marked #22-460 and #22-461. If checking other lights, disconnect the connector with 6 wires #82, 22A, 28, 23, 21, 24.
Connect the positive probe to the connector pin or socket of the light being checked on the front connector.

Wire No. Circuit Pin No.
22-460 Service Stop and Turn Signal light - right. 1
22-461 Service Stop and Turn Signal light - left. 2
21 Service Taillights. 5
23 Blackout Stoplight. 4
24 Blackout Marker. 6
28 Fuel-level Sending Unit. 3
22A Handbrake Switch 2
82 Differential Lock Switch. 1


NOTE — The licence plate wire #26 splices into wire #21 at the left rear of the vehicle.

Turn the light switch, and turn signal lever if necessary, to the position which matches the light being tested. Depress the brake pedal if checking brake lights.

  1. If the meter reads battery voltage, repair or replace the rear wiring harness or the wire at fault.
  2. If the meter shows no reading when checking service stoplights or turn signals, do Test 3.
  3. When checking lights other than service stoplights or turn signals, and the meter shows no reading, see malfunction item 4.

Test 3:
Disconnect the seven wire connector at the turn/brake signal unit. Connect the positive probe to connector pins #2 and then #3 on the wire connector not attached to the signal unit. Move the signal lever for a left and right turn. Ensure light switch is in service drive or stop position.

  1. If the meter shows battery voltage, replace the turn/brake signal unit.
  2. If the meter shows no voltage, do Test 4.

Test 4:
Remove the steering column bottom cover Remove the three, wire connectors from the bottom of the signal lever. Connect the positive probe to the connector socket for wire #463.

  1. If meter shows battery voltage, repair or replace the wiring between the signal lever and the turn/brake signal unit and check the signal lever. Replace, if necessary.
  2. If there is no voltage shown on the meter, do Test 5.

Test 5:
Remove the emergency flasher unit from the dash. Pull the connector socket from the switch. Connect the positive probe to connector socket for wire 460/461.

  1. If there is battery voltage, replace the emergency flasher switch.
  2. If there is no voltage, do Test 6.

Test 6:
Remove the connector from the master light switch. Ensure the directional signal lever is in right or left position and the connector is connected. Connect a jumper wire between sockets “J” and “F” of the wire connector.

  1. If the signal lights now operate, replace the master light switch.
  2. If they still do not operate, repair or replace wire #460/461 between the light switch and the emergency flasher switch.

4. All or some lights do not operate.

Ensure there is battery voltage through the battery master switch by sounding the horn, operating the windshield wipers, or starting the engine.

  1. If there is no voltage, check the battery master switch, the batteries and cables.
  2. If there is voltage, do Test 1.

Test 1: Checking Voltage to Master Light Switch.
Remove the switch panel from the dash. Remove the connector from the light switch. Connect the positive probe to socket “F” in the connector.

  1. If there is no reading, repair or replace wiring harness or wire #15 between the light switch and the tie point.
  2. If there is battery voltage, do Test 2.

Test 2: Checking Voltage Through the Master Light Switch.
Connect a jumper wire from socket “F” to the light that is not working. (Also depress the brake pedal or move the turn signal control lever if checking those lights). See Figure 5-3-2.

  1. If the light that did not work now lights, replace the light switch.
  2. If the light still does not work, repair or replace:
  1. The wiring between the light switch and the brake light switch, if checking the stoplights.
  2. The wiring between the light switch and the emergency flasher switch.
  3. The wiring between the light switch and the rear connector, if checking other rear lights.
  4. The wiring between the light switch and dimmer switch, if checking the headlights.
  5. The wiring between the light switch and either right or left connector, if checking other front lights.


Figure 5-3-1 — Steering System Troubleshooting


Figure 5-3-2 — Master Light Switch Connectors

Socket Wire No Circuit
A 75 Service stoplight switch
B 40 Dash lights
C 22 Service stoplights
D 19 Blackout drive light
E 24 Blackout marker lights
F 15 Battery-positive 24Vdc input
H 21 Tail-lights
J 460/461 Signal lights
K 75A Service stoplight switch
L 491 Park lights
M 16 Headlights
N 23 Blackout stoplight

Figure 5-3-2 — Master Light Switch ConnectorsClick image to enlarge.



Figure 5-3-3 — Instruments and Gauges Troubleshooting

1. All gauges do not work

No voltage to instrument panel.
Test 1:
Remove instrument panel. Disconnect wire #27C, 27D or 27E from either gauge. Turn accessory switch “ON”. Set multimeter to 60 Vdc scale. Connect positive probe to disconnect wire. Connect negative probe to good ground.

  1. If meter reads battery voltage (23 to 25 volts), check instrument panel ground wire #93.
  2. If meter shows no reading, do Test 2.

Test 2: Accessory Switch Wiring
Remove accessory/light switch panel. Disconnect wire #27 from accessory switch. Turn accessory switch “ON”. Connect positive probe to wire #27 terminal “B” on the switch.

  1. If meter reads battery voltage (23 to 25 volts), check wiring between accessory switch and instrument panel #27.
  2. If meter shows no reading, do Test 3.

Test 3: Accessory Switch Wire
Reconnect #27 wire. Disconnect both #11 wires. Connect positive probe to each #11 wire.

  1. If meter shows no reading (0 volts) for either wire, repair or replace wires #11 or #10 between master switch and accessory switch.
  2. If meter reads 23 to 25 volts, do Test 4.

Test 4: Accessory Switch
Disconnect all wires from the switch. Connect an ohmmeter between the terminals “A” and “B” and between “C” and “D”. Turn “ON” the switch.

  1. If there is no continuity in the switch, replace the switch.

2. Battery generator indicator does not work

Test 1:
Remove and connect instrument panel to good ground. Disconnect wire plug from back of gauge. Turn accessory switch “ON”. Connect positive probe to #27E wire.

  1. If meter reads battery voltage (23 to 25 volts), do Test 2.
  2. If meter shows no reading, repair or replace wiring between accessory switch and indicator.

Test 2:
Set the meter switch to the RX1 ohm scale. Connect the meter probes to each of the indicator terminals.

  1. If the meter reads less than 1 ohm, replace the indicator.
  2. If the meter reads more than 1 ohm, remove the indicator from the instrument panel. Clean the surface where the panel and indicator contact and reinstall the indicator. Check it is okay (lets than 1 ohm) and if the indicator still does not work, replace the indicator.


Figure 5-3-3 — Instruments and Gauges Troubleshooting



Figure 5-3-4 — Warning Lights Troubleshooting

1. Warning lights do not work

Defective warning light bulbs.

  1. Check bulb and replace if necessary.

Check for voltage at the relay (see Figure 5-3-6) and check relay.

  1. No voltage, check wiring to relay.
  2. Replace relay if necessary.
  3. Voltage to relay, if relay okay, check applicable warning light sending unit and wiring.

2. Warning light stays on

Defective sending unit.

  1. Check and repair or replace applicable unit.


Figure 5-3-4 — Warning Lights Troubleshooting



Figure 5-3-5 — Horn Troubleshooting

1. Horn does not work

Test 1:
Disconnect wire #25A from horn. Connect meter positive probe to wire. Depress horn button.

  1. If there is voltage, replace the horn.
  2. If there is no voltage, do Test 2.

Test 2:
Remove switch panel. Remove left relay (see Figure 5-3-6). Using meter, check voltage at wire terminal 25.

  1. If there is no voltage, check wire #25 to circuit breaker, circuit breaker and wire #10 from circuit breaker to ignition tie-point. Repair or replace faulty wire or circuit breaker.
  2. If there is voltage, check the continuity through the relay.
  3. If there is no continuity, replace the relay.
  4. If there is continuity, clean or replace the contact in the horn switch or the #25B wire to the switch.


Figure 5-3-5 — Horn Troubleshooting


Figure 5-3-6 — Relays

Wire No Circuit
1 Alternator D+
1A Warning light via 81D
1B Alternator warning light
2A Accessory switch
2B Master light switch
25 Horn circuit breaker
25A Horn
25B Horn switch
81D Warning lights
93H Ground
93K Ground via 93H

Figure 5-3-6 — RelaysClick image to enlarge.



Figure 5-3-7 — Heater Blower Troubleshooting

1. Heater blower does not operate.

Test 1:
Remove the light switch panel from the dash. With accessory switch “ON”, check for battery voltage to and from the circuit breaker. Wire #13 and 13A on the circuit breaker nearest to the light switch.

  1. If there is no voltage to the circuit breaker, check wire 13A to the breaker and the accessory switch.
  2. If there is voltage to the circuit breaker but none from it, replace the circuit breaker.
  3. If there is voltage from the circuit breaker, do Test 2.

Test 2:
Remove the blower switch from the dash. Remove the connector from the switch. With the accessory switch “ON”, connect the positive probe to connector socket wire #13.

  1. If there is no voltage, repair or replace the wire between the switch and the circuit breaker.
  2. If there is battery voltage, do Test 3.

Test 3:
Turn the switch to low speed and then to high speed. Check for voltage at wire socket #29A and then #29.

  1. If there is no voltage, replace the switch.
  2. If there is voltage at only one speed, replace the switch.
  3. If there is no voltage at one or both sockets, do Test 4.

Test 4:
Reconnect the socket connector to the switch and reinstall the switch in the dash. Disconnect wire #29 from the heater motor. With the accessory switch “ON”, connect the positive probe to the wire socket.

  1. If there is no voltage, repair or replace the #29 wire between the switch and the motor.
  2. If there is battery voltage, replace the motor.


Figure 5-3-7 — Heater Blower Troubleshooting



Figure 5-3-8 — Windshield Washer Motor and Pump Troubleshooting

1. Windshield wiper motor does not operate.

Test 1:
Ensure the connector on the motor is secure and socket and terminal pins are clean.

  1. Clean and secure if necessary.
  2. If motor does not run, do Test 2.

Test 2:
Remove connector plug from the motor. Connect the positive probe to the lower left socket of the wire connector. Turn “ON” the accessory switch and the wiper control lever.

  1. If the meter reads battery voltage, replace the wiper motor.
  2. If there is no reading, do Test 3.

Test 3:
Remove the light switch panel. Turn “ON” the accessory switch. Using a meter, connect the positive probe to wire #50A and then to wire #50 of the second circuit breaker from the right.

  1. If there is no voltage at #50A, replace wire #50A from the circuit breaker to tie-point or to #27 of the accessory switch.
  2. If there is voltage at #50A and none at #50, replace the circuit breaker.
  3. If there is voltage at #50, do Test 4.

Test 4:
Remove the steering column lower cover. Pull the connector from the wiper lever. Turn “ON” the accessory switch. Using a meter, connect the positive probe to the socket of wire #53A.

  1. If there is no voltage, replace wire #53A to tie-point or directly to the circuit breaker.
  2. If there is voltage, do Test 5.

Test 5:
Reconnect the connector to the wiper arm Disconnect the wire connector from the wiper lever and the wiper motor under the dash by the steering column. Using a meter, connect the red probe to wire connector socket #3 or wire #53 of the wire coming from the lever. Turn the accessory switch and the wiper lever on.

  1. If there is no voltage, replace the wiper lever or the wire from the lever to the connector.
  2. If there is voltage, replace the wire from the connector to the motor.

2. Windshield wiper operates on one speed only.

Test 1:
Pull connector from the wiper motor. Using a meter, connect the positive probe to either socket of the two upper wire sockets. (Top left for fast and top right for slow.) Position the lever to testing speed. Turn accessory switch “ON”.

  1. If there is voltage, replace the wiper motor.
  2. If there is no voltage, remove the cable and check continuity through the wires.
  3. If wire is faulty, replace wire.
  4. If wire is okay, replace the wiper control lever.

3. Windshield washer does not work (wipers work).

Probable Cause - Fluid reservoir empty.

  1. Refill.

Probable Cause - Fluid hose to spray nozzle or nozzle plugged.

  1. Remove hose from pump and blow through hose to check. Unblock, if necessary.

Test 1:
Remove wire #51 from the pump. Connect meter positive probe to wire. Turn accessory switch “ON” and activate pump lever.

  1. If there is voltage, replace the pump.
  2. If there is no voltage, do Test 2.

Test 2:
Remove the steering column bottom cover. Remove the connector from the wiper lever. Check for continuity through wire #51.

  1. If there is no continuity, check and repair broken wire.
  2. If there is continuity, replace the wiper lever control.


Figure 5-3-8 — Windshield Washer Motor and Pump Troubleshooting



Figure 5-3-9 — Fuel Pump Troubleshooting

1. Fuel pump does not work.

Test 1:
Check for voltage at wire #83 at the fuel pump.

  1. If there is voltage, replace the pump.
  2. If there is no voltage, do Test 2.

Test 2:
Remove the switch panel. Check for voltage to the circuit breaker, wire #83A (farthest breaker to left).

  1. If there is no voltage, repair or replace wiring to accessory switch.
  2. If there is voltage, check wire 83A at breaker. If there is no voltage, replace the breaker. If there is voltage, repair or replace the wiring to the pump.


Figure 5-3-9 — Fuel Pump Troubleshooting



Figure 5-3-10 — Trailer Power Outlet Receptacle Troubleshooting

1. Trailer lights will not operate.

Test 1:
Turn master light switch on. Turn on directional signals and depress brake pedal, if checking these lights. Connect negative probe of meter to trailer receptacle socket “D” and connect the positive probe to the socket of the light being checked (see Figure 5-3-11).

  1. If meter shows battery voltage, problem is in trailer wiring.
  2. If meter shows no voltage, do Test 2.

Test 2:
Leave positive probe connected. Connect negative probe to good ground on frame.

  1. If meter shows voltage, clean ground and check #90 wire.
  2. If meter shows no voltage, replace the receptacle or faulty wire.


Figure 5-3-10 — Trailer Power Outlet Receptacle Troubleshooting


Figure 5-3-11 — Trailer Power Outlet Receptacle Connector

Socket Wire No Circuit
A 24 Blackout marker light
B 22-461 LH stop and flasher light
C 24 Blackout marker light
D 90 Ground
E 21 Parking light
F 23 Blackout stop light
H 490 Blackout marker light
J 460/461 RH stop and flasher light
K,L,M,N — Unused

Figure 5-3-11 — Trailer Power Outlet Receptacle ConnectorClick image to enlarge.