Timmer,
Have you discounted the battery as the source of the problem itself? Any device that is switched won't drain on the switched side if the switch isn't switched??? This sounds goofy, but If you read it a few times it might make sense.
This leaves everything on the batt side of the system. The problem could be a high impedance ground..a short that is going to ground, but not direct enough to make smoke or blow a fuse. Look at obvious places, places where wires run near points that might chafe or rub.
The taillights are switched, but the brake lights aren't. The headlights, dash light and dome light are all switched. A alternator can back feed, but I don't know about a generator.
If the battery is charged, the truck sits for 3 days without being driven, and the battery is now half discharged, it is a drain in a un-switched circuit.
Make sure it isn't the battery...pull and twist the wiring harness as you look for wear spots, and just generally poke around. If nothing develops, then do the "remove-a-fuse" drill.
Stuart
