I was messing around with my truck yesterday and noticed the wire to my left front turn lamp was almost broken off so I re-spliced it. Lights worked fine, moved my trailer around in the yard everything was fine. Jumped in later that night and went to drive into town and as I was heading down my driveway I hit my brake pedal and pop my dash lights and exterior lamps were gone. I thought maybe my splice was shorting out or maybe me tugging on the harness had caused me a problem but after removing the aux battery and tray to inspect the harness I could see no visible damage or short yet I continued popping fuses immediately upon turning on the lights. I thought maybe the socket itself mightve had a short in it so I removed it and again it popped the fuse. I put my continuity tester across the cold side of the fuse and to ground and sure enough there is a short somewhere. I cant think of any reason this mightve happened but it has. I would like to isolate each part of the circuit to try and find the problem but I dont wanna start hacking wires, I dont have a wiring diagram. Any suggestions? It is a 1988 F-250 4x4 7.3 diesel. Thanks for any help or links that may help me.

 

I would start at the trailer harness area. If that was spliced in, that's usually the problem. Or any running boards with lights, or anything added like roof lights would be a place to look. The circuit you are looking at is the running lights circuit and is a brown wire that runs throughout the truck.

There are some main wiring connectors under the brake booster area if you would like to unplug part of the harness.