In this article you will find a description of fuses and relays GMC,
with photos of block diagrams and their locations.
Highlighted the cigarette lighter fuse (as the most popular thing people look for).
Get tips on blown fuses, replacing a fuse, and more.
Instrument Panel Circuit Breaker and Relay Blocks
These circuit breaker and relay blocks are located on top of the instrument panel on the passengerâs side of the cab.
Number | Circuits Protected |
1 | Ignition Switch |
2 | Cigarette Lighter |
3 | ECM Ignition 1 |
4 | Truck Body Controller |
5 | ALDL Connector |
6 | Warning Lamp, Ignition Relay, Blower Motor, Motor Relay, Auxiliary Relay, Power Window Relay, INT Relay |
7 | Room Lamp, Horn, Electric Parking Brake, Radio Back Up, Rear Body Dome Lamp |
8 | Power Window |
9 | Exhaust Brake Back Up, Air Suspension Dump, Differential Lock, Air Dryer, Moisture Ejection Heater, Electric Air Compressor, Power Take Off |
10 | ECM Ignition Power |
11 | Trailer Turn (LH) Lamp |
12 | Auxiliary (Ignition ON) |
13 | Auxiliary (Battery Direct) |
14 | Headlamp (LH) |
15 | Headlamp (RH) |
16 | Headlamp |
17 | Heated Fuel |
18 | Meter Truck Body Controller |
19 | ID Lamp, Marker Lamp, Tail Lamp, Lighted Mirror, Illumination Lamp |
20 | Cool Condenser Fan Motor, Cooler Compressor |
21 | Wiper Motor, Washer Motor |
22 | Heated Mirror, Two-Speed Axle Relay |
23 | Empty |
24 | Blower Motor, Air Conditioner Relay |
25 | Trailer Turn (RH) Lamp, Flasher Unit |
26 | Power Post (Consent) |
Maxi-Fuse Block
Maxi-Fuse block is located outside of the cab at the rear, on the driverâs side.
Name | Circuits/Circuit Breakers Protected |
ST/TURN/HAZ | Stoplamp, Turn Signals/Hazard Warning Flashers |
IGN SW3 | Air Conditioner, Axle, Chassis |
INT/EXT LIGHTS | Parking Lamps, Dome Lamp, Instrument Panel Lights |
HEAD LAMP | Headlamps, Daytime Running Lamps |
AUX WRG | Auxiliary, Parking Brake |
IGN SW1 | Ignition Switch, Washer/Wiper, Crank, Radio |
HYD PUMP | Hydraulic Brake, Brake Pump Motor |
ABS | Anti-Lock Brake System Module |
ELECT TRANS | Ignition Relay |
PARK BRAKE | Parking Brake Motor |
BLOWER HORN | Blower, Horn, Cigarette Lighter, Auxiliary |
TRAILER ABS | Trailer Anti-Lock Brake System, Trailer Stoplamps |
PWR WDO/LOCKS | Power Windows, Power Door Locks |
Relay Blocks
There are three relay blocks in your vehicle.
Relay | Relay block |
A | Relay Block A |
B | Relay Block B |
C | Relay Block C |
Relay Block A
Relay Block A | Usage |
1 | Power Window |
2 | Back Lamp (Reverse) |
3 | High Beam |
4 | Lighting |
5 | Lighting (Low, High) |
6 | Trailer Turn Signal (Left Headlamp) |
7 | Tail Lamp |
8 | Marker Lamp |
9 | Trailer Turn Signal (Right Headlamp) |
Relay Block B
Relay Block B | Usage |
1 | Air Conditioning Condenser |
2 | Air Conditioning Compressor |
3 | Heater Fan |
4 | Ignition Accessory |
5 | Ignition 1 |
6 | Ignition 2 |
7 | Auxiliary |
8 | Horn |
9 | Ignition 3 |
10 | Dome Lamp |
11 | Exhaust Brake |
12 | Power Take Off Control |
Relay Block C
Relay Block C | Usage |
1 | Parking Brake |
2 | Daytime Running Lamps On |
3 | Daytime Running Lamp Off |
4 | Parking Lamps/Daytime Running Lamps |
5 | Neutral |
6 | Stop Lamp |
WARNING:Â Terminal and harness assignments for individual connectors will vary depending on vehicle equipment level, model, and market.
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