Hope it helps

 

yeah i had a hard time with the same situation you had.
that auxillary box, wherever the hell it came from is where i had all my problems very much similar to yours!

i had power to the positive lead, which would charge a battery in a trailer if it were applied but nothing else worked.

i found i had a bad fuse and 1 bad wire to the fuse probably causing the problems. well 2 bad fuses and 1 wire...


oh i should mention i had a bad relay as well. i swapped relays around and my fog lights turned on with the key off. so i tossed that relay and replaced it, not sure exactly what it did or was suppose to do but im damn sure its not suppose to turn the fog's on lol

 

LOL - I went threw hell with them lights once , I ended up choping the harness in the back because the wires got so frail - had to build a new one.

Like that little FOG lights mod that's out there - 5 minutes with a dremal and now my fog' s come on without the headlights if I prefer - I always hated that you coudn't do that from the factory - it was fogs and headlights on the same time or just the headlights - that blew.

Ford didn't provide an aux box explanation in the manual - One manual I have I have says "here's a block of fuses" and has an arrow pointing to it LOL, WTF - So what are they for ? duhhh , no explanation of that in any of the books I have .

Scully has some good links above that explain it.