Cadillac Repair: Creepy/Insane Electrical Malfunction!, cadillac fleetwood brougham, 1994 cadillac fleetwood

Question
Hello, I have a question about a 1994 Cadillac Fleetwood Brougham with the 5.7 LT1.  My door locks click, "lock, and unclock" everytime I tap the brakes.  Also, My a/c shuts off as soon as a tap my brakes or put it into gear.  New compressor by the way.  My turn signals DO NOT work with the headlamps on.  And, if thats not enough madness, my door locks cycle on and off when I turn the wheel with the signal lights on.  I've recently replaced the Optispark distributor.  While doing that, I looked for loose grounds, put didnt find anything out of place.  I'm in the collision industry so I have plenty of people to turn to, but they all want to change the computer.  Any other suggestions?  Or should I just go for the big hit and just swap computers?  Thank you.

Answer
Hi Jeremy,

       A problem like this is rather unusual to just happen out of the blue. If your car was in an accedent and put back together then I could see that some of the strange things would start to happen...but all of those?

       If this car were in my shop I would be asking when these things started happening and if there were any repairs that were done and then the problems occurred. At that point I would be rechecking the repair areas to make sure that I didn't leave a connector unplugged, ground wire unattached or pinch and short out a wire. Especially a ground wire loose under the dash. Also if it was in an accident if there was any mig or arc welding done while the battery or computors were hooked up that could damage them and cause strange things to happen.

      I don't have a Caddy manual in front of me which is what you need to do to trace out all the circuits and see if there is a common ground wire or module such as a body control module that controls everything. It doesn't seem likely that the BCM would malfunction to the point that all your problems are happening but as a last resort you could try one if it were available.

     If the grounds were all good I would physically check all the fuses because a fuse can go open and be backfed by another circuit to make it seem the fuse is good because power is on both sides. All the fuses need to be removed and make sure that they aren't open. Also a relay can short its contacts shut and removeing the relays for the affected circuits might find the problem.

     The place you might actually find a problem although not the whole solution might be a wire that is shorted inside the steering column. I would be tempted to disassemble the steering column to remove the turn signal switch and check its wires as well as all the wires going through the column. As an initial test you could disconnect the turn signal switch connector at the bottom of the column and see how it affects things.

      Good luck with your search because only with the car in front of you and a manual to test things can you hope to find the problem. Bill