Ive got a 1989 740 GL Turbo and a few days ago my windshield wipers turned on all by themselves and wouldn't stop. I narrowed it down to them coming on when the lights are on. If I turn the lights off the wipers stop. I can control the wipers with the wiper switch at varying speeds with the switch if the lights are off.
Well it's stopped raining and I need to drive at night but the wipers wont turn off. I checked the fuses and they all look just fine.
Help!
any suggestions?

 

when circuits cross like that, the #1 suspect is a bad ground somewhere, like in the dash. #2 suspect is bad insulation on a harness wire so the two circuits are touching.

this is assuming someone hasn't done butcherwork trying to repair stuff, and that its all still in stock configuration. if someones butchered wiring, all bets are off.

 

Tighten the ground connector blocks inside the front fenders. 8mm socket, long extension.