headlight problem

Asked by Dec 26, 2012 at 01:24 AM about the 1990 Mercury Grand Marquis 4 Dr LS Sedan

Question type: Maintenance & Repair

1990 (mfg date 11/89) Mercury Grand Marquis, 5L, MFI, loaded

Cut to the chase:  what is the correct multi-switch (dimmer) for this vehicle?  O-Reilly's says (and gave me) a BWD #S3217.  I think it is wrong.  Now the story:

About a year ago the brights began going out (all lights out).  Switching to dims brought them back.  Thinking it was the multi-switch, I bought another.  A previous vehicle ('79 Toro) had a similar problem that turned out to be the multi-switch partially melting.  As it was near the end of winter and I had little time, I put the switch in the trunk and drove on dims.  Friday, on the way home for Christmas weekend (of course) the lights started going off entirely.  Fiddling with multi-switch got me home.  I could hear a clicking behind the dash as they turned on and off.  I have since read that the problem may be the headlight switch (WAH).  The wah is because I replaced the multi-switch and disassembled the old one to diagnose problem.  All I found was some carbon blacking on the contacts.  This switch is built much better than the Toro switch.  I see no evidence of plastic melting.

Anyway, problem now is that I now have daytime running lights (didn't before), and the battery drains overnight.  Disconnecting the battery and putting an ammeter in series, I get a 1 amp drain with doors shut, no key in ignition, trunk shut, and hood bulb unplugged.  Oh yeah, when I say I have daytime running lights, it doesn't matter whether the headlight switch is pushed in or pulled out (yes, old style) the lights come on as soon as the key is turned and will not turn off (key out, waited over a minute) until the battery is disconnected (stay off after battery re-connected until key turned on).  The only thing I have done during this project has been to remove the old switch and replace it with the new.

I suspect I was given the wrong switch (ya think).  I am thinking about getting a battery cutout switch tomorrow so I can drive to work (30 miles each way) and not have battery drain down while at work, but am concerned that the incorrect switch may cause other problems.


Really, any assistance will be greatly appreciated.


1 Answer


Make sure that they gave you the switch with the headlight delay. There are two switches. One for cars with headlight delay, one without. It seems like you got the one without, that's why the lights are not going off. Go back to reily's and have them double check it for you. Most of these autoparts stores nowadays have kids working there that don't know didly-squat about cars, especially one that's probably as old or older than they are. Kenny/MrBlueOval

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