[PDF] WIRING DIAGRAMS - 73-87ChevyTrucks. Classic Chevy WIRING HARNESS AND WIRES Every wire is a specific size with colored or striped insulation that is indicated on the wiring diagrams. Insulation colors help to trace circuits and to make proper connections. Abbreviations and symbols used for indicating wire insulation colors and patterns are as follows:[PDF] WIRING DIAGRAMS - 73-87ChevyTrucks. Classic Chevy WIRING DIAGRAMS DESCRIPTION . The main wiring diagrams are laid out so that the After the main diagrams are systems diagrams. diagram corresponds in position to the actual wiring in These supplemental diagrams simplify the circuit trac the vehicle. Therefore, the headlight circuitry is located ing for the technician.