1999 GMC C-SERIES wiring

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2-44
Press the top left switch to turn on your:

Parking Lamps

Marker Lamps (unless your vehicle has the optional
marker and clearance lamps switch)

Taillamps

Instrument Panel Lights

License Plate Lamps
Push the bottom left switch to turn on the headlamps, as
well as all of the lamps just listed. Push the switch
marked with the ªOº symbol to turn off your lamps.
Move the thumbwheel to the right of the off switch
down to dim your instrument panel lights. Moving this
wheel up makes these lights brighter. Moving it all the
way up will make the interior lamp come on.
A circuit breaker protects your headlamps. If you have
an electrical overload, your headlamps will flicker on
and off. Have your headlamp wiring checked right away
if this ever happens.Headlamps On Reminder (If Equipped)
If you have this system, a tone alarm will sound when
your headlamps and/or parking lamps are turned on and
your ignition is in OFF, LOCK or ACCESSORY.
Daytime Running Lamps (If Equipped)
Daytime Running Lamps (DRL) can make it easier for
others to see the front of your vehicle during the day.
DRL can be helpful in many different driving
conditions, but they can be especially helpful in the
short periods after dawn and before sunset.
The high and low
-beam headlamps will come on at
reduced brightness in daylight when:

The ignition is on,

The headlamp switch is off and

The parking brake is released.
When the DRL are on, only your low
-beam headlamps
will be on. The exterior lamps won't be on. Your
instrument panel won't be lit up either.
When it begins to get dark, your DRL indicator light is a
reminder to turn your headlamp switch on. The other
lamps that come on with your headlamps will also
come on.
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5-3 Hazard Warning Flasher Switch
(If Equipped)
With some options, such as U86-trailer wiring or
RQ3
-tractor application, you will have this switch.
This switch replaces the hazard switch mounted on the
steering column. It is mounted in the instrument panel,
usually to the left of and below the steering column.
Pull the switch out to make your front and rear turn
signal lamps flash on and off. A light next to the switch
will also flash. Push it back in to turn off the flashers.
The turn signal lamps won't flash if you're braking.
This switch works no matter what position the key is in,
and even if the key isn't in the ignition.
When the hazard warning flashers are on, your turn
signals won't work.
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6-68
Electrical System
Add-On Electrical Equipment
NOTICE:
Don't add anything electrical to your vehicle
unless you check with your dealer first. Some
electrical equipment can damage your vehicle
and the damage wouldn't be covered by your
warranty. Some add
-on electrical equipment can
keep other components from working as
they should.
Headlamp Wiring
The headlamp wiring is protected by a circuit breaker in
the light switch. An electrical overload will cause the
lights to go on and off, or in some cases to remain off.
If this happens, have your headlamp wiring checked
right away.
Windshield Wiper Fuses
The windshield wiper motor is protected by a circuit
breaker inside the motor and a circuit breaker in the fuse
block. If the motor overheats, the wipers will stop until
the motor cools. If the overload is caused by an
electrical problem, be sure to get it fixed.
Fusible Links
A fusible link is a short piece of wire several gage sizes
smaller than the circuit it protects. It will melt in an
overload situation, opening the circuit.
Your starter relay and other circuits have these fusible
links. The size is printed on the insulation. If the insulation
is burned beyond recognition, consult your GM dealer for
the proper size. Replace a fusible link with one of the
same size and insulation type. Fusible link insulation is a
special purpose high
-temperature material.
The hydraulic brake booster motor feed circuit and
starter relay circuit are protected by a fusible link.
Vehicles with a diesel engine have a fusible link for the
intake heater feed circuit. Vehicles equipped with an
electronically controlled diesel engine also have a
fusible link for the engine control unit.
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6-69 Power Windows and Other Power Options
Circuit breakers in the fuse panel protect the power
windows and other power accessories. When the current
load is too heavy, the circuit breaker opens and closes.
This protects the circuit until the current load returns to
normal or the problem is fixed.
Fuses and Circuit Breakers
The wiring circuits in your vehicle are protected from
short circuits by a combination of fuses, circuit breakers,
maxi
-fuses and fusible links. This greatly reduces the
chance of a fire caused by an electrical problem. There
may be a fuse taped to the wiring harness inside the
battery box and one near the generator also taped to the
wiring harness.
There are two circuit breaker/fuse blocks in your
vehicle: the instrument panel circuit breaker block and
the maxi
-fuse block.
Instrument Panel Circuit Breaker Block
This fuse block is in the lower portion of the instrument
panel, to the left of the steering column.
To open the door, pull up
and outward on the recessed
door handle and the door
will snap out.
To install the door, place the lower door into the bottom
retainer and push the top of the door in until it snaps
into place.
If you ever have a problem on the road and don't have a
spare circuit breaker, you can borrow one of the correct
value. Just pick some feature of your vehicle that you
can get along without
-- like the radio or cigarette
lighter
-- and use its circuit breaker if it is of the value
you need. Remember to replace the circuit breaker as
soon as you can.
These circuit breakers are non
-cycling; do not replace
them with cycling circuit breakers. Also, don't use
circuit breakers of higher amperage than those indicated
on the circuit breaker block.
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6-70
Name Circuits Protected
HYD BRK Brake Pump Motor Relay
HYD BRK Brake Alarm ModuleName Circuits Protected
B/U IGN3 Fuel Filter Relay, Blower Motor
Relays, ABS Power Relay,
Back
-Up Lamps, Auxiliary Wiring
Relay, IGN 3 Relay, Power
Window Relay, Vehicle Interface
Module, Transmission
Temperature Gage
STOP Stoplamps
WASH/WIPE Windshield Wipers/Washer,
Accessory Relay
DOME/PNL Dome Lamp, Radio Receiver,
Instrument Panel Lights,
A/C Controller,
Headlamp/Seatbelt Module
BLOWER Blower Motor
A/C A/C Clutch Compressor,
A/C Controller
TRN/HAZ Turn Signals, Hazard Flashers
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6-71
Name Circuits Protected
CHAS Exhaust Brake, Air Suspension
Dump Valve, Air Dryer, HYD
ABS ECHU
PARK LP Auxiliary Wiring, Air Conditioner
Controls, Parking Lamps, Turn
Signals, Taillamps, Stoplamps,
Marker Lamps, Trailer Running
Lamps, Lighted Mirrors, Radio
Receiver, Mirror Clearance Lamps
HORN Horn/Diagnostic Connector
PRK BRK Parking Brake Module
FUEL Heated Fuel Filter (Diesel
Engines) or Fuel Pump
(Gasoline Engines)
AXLE Heated Mirrors, Radiator Shutters,
Tw o
-Speed Axle Motor,
Tw o
-Speed Axle Switch
MRKR LP Roof Marker Lamps,
Trailer Marker Lamps,
Marker Lamp RelayName Circuits Protected
CIG/AUX Cigarette Lighter,
Auxiliary Power Jacks
AUX Auxiliary Wiring Relay
IGN RLY/VIN Vehicle Interface Module
(Diesel Engines) or Generator,
Coil, Injectors (Gasoline Engines)
WDO Power Windows
CRNK Starter Relay
IGN SW Instrument Panel Cluster Telltales
AUX Auxiliary Wiring
RDO Radio, Auxiliary Wiring
DR LK Power Door Locks
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9-5
Gages
Air Pressure 2-69 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine Coolant Temperature 2-61 . . . . . . . . . . . . . . . . . . . .
Engine Oil Pressure 2-65 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filterminder 2-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel 2-68 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hourmeter 2-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oil Pressure 2-65 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Speedometer 2-53 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tachometer 2-54 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transmission Temperature 2-69 . . . . . . . . . . . . . . . . . . . . . .
Voltmeter 2-56 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Guide en Fran†ais ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hazard Warning Flasher Switch 5-3 . . . . . . . . . . . . . . . . . . .
Hazard Warning Flashers 5-2 . . . . . . . . . . . . . . . . . . . . . . . . . .
Head Restraints 1-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Headlamps 2-43 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High/Low Beam Changer 2-34 . . . . . . . . . . . . . . . . . . . . . .
Wiring 6-68 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Heating 3-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Highway Hypnosis 4-21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hill and Mountain Roads 4-22 . . . . . . . . . . . . . . . . . . . . . . . . .
Hood
Access Panels 6
-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Checking Things Under 6-9 . . . . . . . . . . . . . . . . . . . . . . . . .
Latches Check 7-27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Horn 2-31 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hourmeter Gage 2
-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hydraulic Brake Warning Light 2-58 . . . . . . . . . . . . . . . . . . . .
Hydroplaning 4-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition Positions 2-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inflation, Tire 6-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inspections
Engine Cover Check 7
-27 . . . . . . . . . . . . . . . . . . . . . . . . . .
Underbody 7-27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Instrument Panel 2-50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Circuit Breaker Block 6-69 . . . . . . . . . . . . . . . . . . . . . . . . .
Cleaning 6-61 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cluster 2-52 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Intake Heater Indicator Light 2-63 . . . . . . . . . . . . . . . . . . . . . .
Inter-Axle Differential Lock Control 2-40 . . . . . . . . . . . . . . . .
Jump Starting 5-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Keys 2-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Labels
Certification/Tire 4-28, 6-67 . . . . . . . . . . . . . . . . . . . . . . . .
Service Parts Identification 6-67 . . . . . . . . . . . . . . . . . . . . .
Vehicle Identification Number 6-67 . . . . . . . . . . . . . . . . . . .
Lamp and Bulb Data 6-74 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lamp Check 7-26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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9-10
Warning Devices 5-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Warning Lights and Gages 2-55 . . . . . . . . . . . . . . . . . . . . . . . .
Warranty Information 8-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Washer Fluid, Windshield 2-35, 6-29 . . . . . . . . . . . . . . . . . . .
Washing Your Vehicle 6-63 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Weatherstrips 6-62 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wheel
Alignment 6
-51 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Nut Torque 6-52, 6-74 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Replacement 6-57 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tightening the Wheel Nuts 6-52 . . . . . . . . . . . . . . . . . . . . .
Windows 2-30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Manual 2-30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power 2-31 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Windshield Washer
Fluid 2
-35 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fluid Level Check 7-23 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Windshield Wipers 2-35 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Blade Cleaning 6-62 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Blade Replacement 6-43 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuses 6-68 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low Speed Delay 2-35 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Winter Driving 4-24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wiper Blade Check 7-24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wiring, Headlamp 6-68 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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