This is the original wiring diagram printed by GM for dealer mechanics. You can follow the wiring in your truck from bumper-to-bumper. It will help you to understand connector configurations, and locate & identify circuits, relays, and grounds. Although the schematic is in black and white, the color of each wire is noted. You will not find this diagram in your shop manual. The schematic measures 8.5" x 11" when folded up, and opens up to 11" by 38". The diagram pictured is an example of this type when folded, but is not the actual diagram for your vehicle. Buy now for the best electrical repair info - the factory wiring diagram.
1979 GM Wiring Diagrams Medium/Heavy Truck MD17880
This item is original.
11.00 x 8.50 x 0.10 inches
Covers forward control chassis models P4T with in-line 6 gasoline engines. These are forward control chassis typically used for stepvans, motorhomes, and buses. To verify that this is the correct diagram for your truck, you can check your VIN code. The 4th digit should be a T for the forward control chassis, and the 6th digit should be a 9 to indicate the 1979 model year.
1979 Chevrolet 40-60 Medium Duty
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1979 Chevrolet 40-60 Medium Duty 1979 GMC Motorhome Chassis 1979 GMC Series 4500-6500