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Ford Crown Victoria/Mercury Grand Marquis Electrical/Lighting



  • i'm looking for a junction in the wiring harness because i can't reach the individual door button switches in the door frames? only cause for all of the interior lites to remain on would be if the headlight switch is turned to the right. any other suggestions?
  • My mercury just started developing electrical problems today. I first noticed that the clock went out as well as the cig lighter and power point. I went out tonight after dark and realized too I have no dome light, head lights or parking lights. the turn signals and radio and everything else works ok. The only thing I have not checked yet is the wipers. I checked all the fuses in the cabin and they all check out ok. Any suggestions? I don't have much money but if someone can offer advice on where to look for the prob i will try to dig into it myself and see if i can fix it relatively cheap rather then pay a Ford dealer. Please help. I need my car to get to work and its is dark when i get off work, so i need working headlights
  • euphoniumeuphonium Great Northwest, West of the Cascades.Posts: 3,425
    On the driver's side of the engine bay there is a Black box containing a set of circuit breakers. Check it out according to your Owners Manual.

    Try to reset the on board computer by disconnecting the Negative battery cable for a few minutes and then reconnecting it.

    If you're good at removing the cable, remove both cablrs and clean the terminals with a post cleaner & use the wire brush end to clean out the center of the cables.

    Corrosian diminishes energy to the accessories.
  • My auto headlights on my 2003 Merc Grand Marquis do not work consistently. They turn on intermittently and rarely when I need them at night. If I run the emergency flashers while driving at least 2 minutes they sometimes come on. Also, if I use the security keypad on my door to unlock the car they sometimes come on. I have been driving while holding the "flash to pass" control and will get a high beam that works for now. If I push the high beam control forward toward hood nothing happens. I'm out of work and am looking for some "do it yourself" suggestions. I'm not afraid to do the work but do not know my way around this car.
  • Thanks njadams. I will give them a try and post back when I run through the process.
  • jim416jim416 Posts: 1
    I have a 98 crown vic that the headlights quit working. the flash to pass will turn on the headlights when held but not the switch. I have tried a different lcm from two different lcms from unwrecked cars from junk yard. still no luck. when i turn the light switch to parking lights I hear the relay click and the parking lights come on. when i turn the switch to lights I hear the relay click but no headlights. since the car was new i have run it with the photo sensor covered with electrical tape to make it think it was dark so the lights would be on all of the time. i don,t know if there is another relay that may be having a problem. any ideas ?
  • My 2003 Grand Marq. mercury has been diagnoised as having a malfunctioning "lighting control module". I paid a mercury dealer $91.50 for this info. The same dealer wants $608.50 more to repair the problem. I need to know if this total of $700.00 is a reasonable price for this and,if not, what would be a reasonable charge. My lights turn off unexpectedly but shortly come back on. I am an older guy (WW II veteran) and on a limited income. Any helpful info would be greatly appreciated.
  • euphoniumeuphonium Great Northwest, West of the Cascades.Posts: 3,425
    Until the two fuse locations are checked out by an independent auto electrical tech I would hesitate on buying a new module. I believe there is a Black circuit breaker box under the hood. Hopefully, that is your source of the lights going out as that breaker opens and closes from time to time. The other fuse location, under the dash, contains fuses of different colors and when when of them blows - that's it until it is replaced. Since your lights come on later, I would inspect the breakers in the Black box under the hood.
  • My mercury grand marquis wipers do not work. I replaced the wiper switch because a mechanic told me they go bad a lot and they still do not work. Does anyone have a idea of what it could be?
  • 1999 merc grand marquie (pos) replaced the LCM , door striker switch,re adjusted door strikers and cleaned contacts in the LCM and the stricker switch. and the damn courtesy light still comes on random leaving the car dead every morning!!!! any insight to this problem would be greatful.
    oh ya did i mention thats about a thosand dollars in parts so far chasing a bug that will not squash
  • I would bet it's your driver's door, exterior touch button, key pad(that is if you have one). Pull the interior door panel off and unplug the key pad. They get corroded in there and cause just what you are experiencing. Unplugging it should end your problems with no ill effects. You could replace the key pad if you actually use it.
  • euphoniumeuphonium Great Northwest, West of the Cascades.Posts: 3,425
    I don't know how this works, but sometimes disconnecting the battery for a couple of hours enables the "gitzensnorkle" to reset itself. Might be worth a try before removing the door panel.
  • My '01 Grand Marquis just developed an unusual electrical problem. It started during a mountain trip. The first problem was the ABS and Trac Ctl indicators on the dash came on. Then a very unusual problem appeared - the high beam indicator illuminated and both turn signal indicators came on, but dim. The headlights and front running lights don't come on(relays clicks) The tail lights and brake lights work(allowed me to get home...) The turn signals work sometimes - blink very fast. On the highway, the turn signal and high beam indicators go out around 50mph - the A/C compressor will work when they go out. Windshield wipers work, washer doesn't. No engine codes(nor check engine light). Assume some ground issue or some control module failed?
  • raszmanraszman Posts: 4
    Found the electrical problem... right front fender was replaced a couple of months ago during paint job and they failed to tighten a ground wire that attaches to the fender inside......ABS light remains on - next on the list to troubleshoot!
  • speaquespeaque Posts: 1
    I'm having the same problem with the same year Grand Marquis. How did you resolve it? Thanks.
  • My mechanic replaced a "multi-function" switch located underneath the steering column and that worked for me. Cost me $200 for parts and labor.
  • raszmanraszman Posts: 4
    I was "fortunate" that I found the body shop's failure to tighten the ground wire prior to replacing parts. The ABS indicator appears to be a separate coincidental issue. I'll clean off the sensors as others in this forum have recommended and if that fails I will have the ABS codes read I guess.
  • yooper88yooper88 Posts: 2
    I have a 2000 Mercury Grand Marquis. The ignition buzzer, turn signals, parking lights, headlights, dome light and hazards are not working. The brake lights do work. I checked the fuse panel info and could not find any relay or fuse that links all these indications together. Did check every fuse and did not find any bad. I don't have any schematics to see what all these have in common. Thinking possibly a bad wiring harness connector, maybe on steering column, ignition switch or battery (original). Anyone seen this problem before?
  • i have a 2003 grand marquis. went to get an emissions sticker and the guy couldnt get a reading from the computer. told me there was no power going to the computer plug. checked all my fuses and cant find any fuses blown. manual doesnt tell you which fuse powers the data link or obd so i checked them all. not sure if a relay powers it. anyone have any ideas what to check? i have 60 days to correct this before my sticker is bad. Thanks in advance, john
  • im sure you got it fixed by now but if you ever hear of anyone else having this problem, tell them to go to ebay. i bought a LCM (lighting control module) for $150. on ebay. it has a lifetime warrenty. very easy to install to the right of the steering colum under the dash. returned old LCM in a self addressed envelope that came with the new LCM. within days he credited me $50. so i only paid $100. all is good!
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 57,595
    Well before we panic here, it might be a good idea, just as a double-check, to try another scanner, say from Autozone or O'Reilly (where they usually do it for free).

    There are tests, called "Pinpoint Tests" to determine if you have some damage in the harnesses related to the PCM or the Datalink connector, or some other component failure, but you'll have to go to a repair shop that knows what they are doing. You could have a short or bad ground in some harness, yes.

    But first see if some other scanner can read.

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  • thanks for your reply. i did go to autozone, they plugged in their handheld computer and it also had no reading at all. the gentleman there said the same thing, without power to that connector he cant get a reading.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 57,595
    I searched to see if the data link was fused but couldn't find anything. ON some cars it is fused. Have you disconnected your battery in the last couple hundred miles?

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  • havnt disconnected the battery for a long time. ive searched my manual and cant find any fuse or relay labled as the computer fuse or relay. any idea how to figure out which one powers it? or maybe it doesnt have a fuse for it? nobody seems to know anything about this problem. no ones ever heard of this before.......just my luck.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 57,595
    Well yeah the problem does come up but often, say on most GM cars, there's a fuse that controls it. If there isn't, then someone has to test the various pins in the connector link and figure out why there's no power to the data link. These systems are not as standardized as one might think. I have heard that on some cars when certain components fail they will also knock out the data link, but again, I can't find anything specific to your make and model.

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  • suavemikesuavemike Posts: 1
    Did you figure out what the issue was? I am having the exact same problem. A dime fell into my 12v cig lighter and shorted it out. I replaced the fuse to the cig lighter but now my dome lights, headlights, and clock don't work. Turn signals and radio and everything else work fine. Just the same as your vehicle. So I'm guessing what ever it is that shorted out is the same on both our vehicles. Any info would be greatly appreciated!!!
  • fordgirl4fordgirl4 Posts: 3
    I spent around a grand and still had the same problem. I ended up just taking the bulb out of the dome lignts, ant turning the light switch to off. I still have a dome light if I turn the switch on, so I have not had to worry about the dome light and lights coming on during the night and running my battery down. I realize this is not a fix, however it was cheap and it works!
  • euphoniumeuphonium Great Northwest, West of the Cascades.Posts: 3,425
    "I ended up just taking the bulb out of the dome lignts, ant turning the light switch to off. I still have a dome light if I turn the switch on"

    If the bulb is out of the dome, how do you get a light from just turning the switch on??? ;)
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