Here's a trick I use for tracking down faults in car and truck wiring. Maybe it will help you.
Take one cable off the battery and connect a 12 volt
test light between the cable and battery post. With everything turned off the light should be dark. If it glows it means there is a current draw.
Take out the fuses one by one. When you get to the one that shuts off the test light, that is the circuit that has the problem. By doing this you narrow down the problem and track it down.
If you still can't figure out exactly what is wrong, at least you can disconnect the faulty part and leave it off until you get to a service tech. It will save him time too.