'98 Grand Marquis, Danged Lights not Working

[V-8Fan]

I had this problem a while back. I checked all the fuses and found nothing wrong. Then I came here, where there is often very good info. Well, the consensus seemed to be that the Lighting Control Module has to be replaced when this problem crops up. So, I had my LCM "rebuilt" for $100 by some outfit in Tennessee. When I got it back I installed it and...same stinkin' problem! Those folks in Tennessee got my money for nuthin. It happens.

So...I removed the Multi-Function Switch (we called 'em turn signals" in the old days) and with great trepidation and fully expecting parts to go flying all over the room, I took the thing apart. There was some stuff all over the contacts that looked like it had been grease at one time, and I would assume it was supposed to preserve all the iddy-bitty contacts and stuff in the switch. The stuff had hardened so I removed a good deal of it with a solvent and reassembled the switch. When I reinstalled it in the vehicle, I was pleased to see everything working again.

So...I don't think the first thing to suspect is the LCM. There's not a danged thing you can do to repair it---it's designed and built by Motorola, and even a seasoned electronics tech with well over 25 years experience such as myself ain't gonna figure it out and you couldn't get the parts to fix it even if you knew which ones to replace. Removal and disassembly of the MFS is simple enough, and anyone handy with tools ought to be able to clean the contacts within it. If that won't fix the problem, then start looking at the LCM.

[pcmos]

Can you describe the problem you were having before you rebuilt the multi-function switch? I'm helping my father diagnose his 2003. He says that while he is driving with the headlights on, they will simply shut off without warning. I have the factory shop manuals for the car and the factory wiring diagrams.

After tracing the circuits I can't quite see how a poor contact in the MFS could cause the headlights to shut off. I can certainly see how a poor contact in the fuse box or in the headlight switch (dash mounted) could cause the headlights to malfunction.

In the case of my father's car, he reports that he can activate the hi-beams by pulling back on the multifunction lever to activate "flash to pass." When the headlights fail he has to hold the MFS lever back continuously.

My father's car was recently involved in a rear-end collision and the problem only started to crop up after he got the car back from the body shop. I suspect perhaps the impact jarred something in the LCM which is causing the failure. It;s much cheaper/easier to check the multifunction switch first I guess.

[lesab92]

Our 2001 Mercury Grand Marquis does this every once in awhile. While driving in a heavy rain storm yesterday, the lights just went off. It has done this one other time. I'm wondering if the culprit is the LCM? Seems like these Ford products seem to have similar problems as I've seen a posting on the Crown Vic site that has a work around for the relay on the circuit board of the LCM if that relay burns out.

[vtwindave]

just purchased a 2000 gm, trying to learn about it. where is the lcm located? thanks for any info.

[lesab92]

Here is a link to similar post on Ford Crown Vic forum. May be helpful.

http://www.automotiveforums.com/vbul....php?t=1060312