1996 Ford Ranger-Same problem with lights, wipers. I have determined that dome, glove box, cargo, map, underhood lights and wipers share a main power feed. They have started working intermittantly again. I have been able to verify when power is lost the relays in the Power Distribution Box for the wipers have no power to them. Everything else in the PDB has power. Acts like a chemical fuse is going bad. All wiring diagrams I find in after market manuals is incomplete and /or inaccurate.

I share your frustration. Have tried to find wiring diagrams in the books that I get at the auto store and also in searching online. Have you tried your local library?