I bought this very used 1984 f150 about 5 years ago. Someone had put it a 350 in it and rewired it. Lots of wires that don't go anywhere, just taped off. Last week I drove it home, next day it wouldn't start, no lights, nothing. Battery and cables are good. Appears a wire from the harness to the solinoid was fried. In the process of trying to track down a possible open wire/short the entire harness started to disintegrate on me. I probably need to get another one, but need a diagram to know what wires go where. Any ideas on what wire this was and/or where I could get a diagram and a different harness?

 

A smaller wire hooked to the solenoid underneath the large wire going to the battery +? If so, this is the main electrical feed for the whole truck.

The factory wiring diagrams are made by www.helminc.com. See if they have any in stock. The cheapo haynes manual has a pretty good set in it for 84-86 trucks.

If you want to start experimenting and troubleshooting the wiring, hook a small battery charger up to the battery cables and disconnect the battery. The battery charger has a circuit breaker in it, so if there is a problem, the wiring will not melt till you get it sorted out.