2000 mercury grand marquis Headlight puzzle


Old 10-19-14, 08:17 PM
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Question 2000 mercury grand marquis Headlight puzzle


I love my car but have a problem that I've been unable to fix and would love some advice.

Inconsistently but after about 10-30 of driving my headlights go out and every dash light starts to flash at a rate of about 10x per second. It seems like a short circuit to me. During the short a buzzer is also going on/off. Since this happens alot I have tried everything to see what affects it. The only thing that stops the 'short' is to pull the high beam level towards the drive. While doing this all dash lights return to normal and the buzzer stops. The headlights do not come back on nor do the high beams. No position of the actual lighting switch makes any difference. To fix the problem I nave to turn the lights off for a minute and turn them back on. After doing this one to three times they come back on. Not ideal for nighttime driving.

I took the car to the local ford dealer who said I needed a new lighting control module for $600 part + $130 labor after the $140 diagnostic charge. I had my lighting control module repaired for $45 from my airbags company. I put the repaired unit in and it still does the same thing. A neighbor has almost the exact same car as mine and let me try his part. It did the exact same thing so it does not appear to be the LCM.

It acts like a short but the dealer says that unless I do the repair thru them for close to $1000 they can't help. I told them that I've tried 2 more LCMs and that the problem continues. My car does not qualify for Ford LCM replacement and its looking like that is not the problem now that I have tried 3 of them and the same problem exists.

I'm looking for any suggestions. I'm pretty handy on repairs but not with cars.

Thank you,
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Old 10-19-14, 08:42 PM
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when you say you replaced the LCM where was this part? im only asking to insure you swapped the right part. aside that it to me sounds more like a headlamp switch to me. i have owned and worked on many the connector burns out at the switch. you have to replace both to fix it long term.
Old 10-19-14, 08:56 PM
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Interesting problem and it seems a load of people have experienced it. While looking around at different tech sites I came across the following thread. One of the posts had an "in detail" explanation of the Ford remedy. Apparently the warranty on this issue or at least the module was extended to 250k miles and 15 years. Give it a read.... it may be of some help.

Mercury Grand Marquis Questions - is the light switch the same as the light control module.
Old 10-20-14, 09:44 AM
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Join Date: Oct 2014
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It above the gas pedal. I'm sure that I did replace it as I had to send it in to get repaired and then used my neighbor's working one (exact same car almost). Same results. It has three large multi connectors on it.

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