I have a 74 dually and the running lights on the roof needed bulbs so I put new bulbs in and everything worked good for about 5 minutes then all the lights went out. I replaced the fuse and still nothing. I been checking the grounds but it's hard because the stock harness is pretty hacked up. I was wondering if anyone had pictures or diagrams of the stock harness for the tail lights, brake lights and towing package.

I have alot of wires cut and spliced together. I can't seem to find the wiring diagram for the lights for this year truck. The reverse lights work on the truck but that's it. I have done a good amount of wiring on cars but I the way this wiring has been hacked up is just one big headach.

Forgot to say the dash lights also went out with the brak and tail lights. the only lights I have working in the truck are the headlights. No other lights are working. I checked all the bulbs and their all good.

best guess is a ground. ive had similar symptoms with vehicles and that shit is annoying. sorry im not that much of a help. good luck.