My father has a 1994 E34/M50 that keeps blowing the fuse for the internal lights. It seemed as if the problem was with the switch for the trunk lid, but it doesn't appear that's the case. Apparently there's a short somewhere, but we're having trouble tracking it down. Here's what has happened:
He would go to the gym, open the trunk, take out his bag and all was well. The trunk light would work. Close the trunk, go into the gym, come out, open the trunk and the light wasn't working. Fuse blown. This has happened several times. Yeah, we know, if the fuse keeps blowing, then something's doing it for a reason. But he's been letting this happen to try to diagnose the problem. (He's not stupid with this as he's an electrical engineer by trade.) He's tried moving around the wire harness around the trunk hinge to reproduce the problem, but no dice.
Since the problem seemed to be associated with opening and closing the trunk he disconnected the trunk switch for the light to see if the problem was with the switch itself. Fuse still blows. So that's not the problem.
The latest experiment involved locking the car and then pulling on the driver's door to turn on the interior lights. (Trunk switch is still disconnected.) Lights turn on then eventually fade out as they're supposed to. He does this three or four times and things work fine. The next time he does it, the lights don't turn on. Fuse is blown.
So the problem is elsewhere. He has a Bentley manual and has the wiring diagrams to refer to, but he doesn't know where to start looking. Does anybody know where the problem lies?