Model Condition Price Qty  
MD7749 1973 Very Good $29.00
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.
General Motors
"Cab, Engine and Chassis Wiring - HN/JN-9003; 9500 MD-7749"
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This diagram covers 1973 GMC and Chevrolet 90-95 9000-9500 Conventional models also known as HN or JN, equipped with the Cummins NHC 250 diesel engine.To verify that this is the correct diagram for your truck, you can check your VIN code. The 2nd digit should be either an H or an J for heavy duty conventional cab. The 3rd digit should be an N to indicate the Cummins NHC 250 Diesel and the 6th digit should be a 3 for the 1973 model year.
1973 Chevrolet 70-90 Series Heavy Duty
1973 GMC Series 7500-9500
1973 Chevrolet 70-90 Series Heavy Duty 1973 GMC Series 7500-9500