Dome, underdash and cargo lights - Chevy Message Forum Aug 16, 2012Does anybody have a wiring diagram that shows this circuit? I am attempting to get my dome and cargo lights to work but am having no luck. I believe the ground wire to the dome light is cut, but i cannot find where the wires go after they go into the ceiling. Its on a 1979 crewcab pickup. Thanks. Dome Light Wiring Pictures - Chevy Message Forum Jun 24, 2012I just got done wiring the dome light in the 50. The blub used is a double pole type which means the metal case of the bulb itself is NOT used as a ground source to light the bulb. Just the bottom poles. (number 90, 12 volt bulb I think) A single positive wire runs to the dome light Gmc Truck Wiring Diagram Schematic - ALLDATAdiy ALLDATA gives you all available wiring diagram schematics, updated four times a year to meet changing factory service and repair information. We are the leading source of Professional Diagnostic and Repair Information used by over 75,000 repair professionals. We offer both one-year and five-year subscriptions for our GMC Truck manual.