I have been given a 1990 Cadillac Sedan Deville. Nice car, except when you turn on the headlights the windshield wipers come on, when you turn on the windshield wipers the headlights flash, when the cruise control works the radio doesn't and when the radio does work, the cruise doesn't. I've been told that the problem is a Multi-function switch..but I don't find anything about a multi-function switch for that year model. I've also been told the wiring harness needs to be replaced..but no one really seems to know what to do to fix it or how much it will cost. I can't afford a real expensive fix, nor can I afford for the problem to get worse. Any ideas??

 

My guess is someone fooled with the wiring to the switch or in that wiring harness. The Mulit-function switch is the lever on the left side of the steering column that you use to operate the cruise/headlight high/low beams and the windshield wipers. The wires are mis-terminated most likely.Hope this helps some......

 

Mods? Grounds next choice. You may need FSM to figure it out.