Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

Ford Crown Victoria/Mercury Grand Marquis Electrical/Lighting



  • euphoniumeuphonium Great Northwest, West of the Cascades.Posts: 3,305
    You may have your "automatic" light switch on. There is a sensor on top of the dash that governs when the lights go on. If that sensor is covered up, the lights will switch on. Naturally, the sensor detects very dark days and nights.

    The switch also may have the feature of "delayed off" which turns them off after removing the key from the ignition.

    As to the fast idle, I think it is factory set.
  • thanks. I have the switch turned off. I haven't seen the sensor on the dash. I wonder if I can replace the headlight switch with one that doesn't have the delay?
  • The 98 GM starts to turn over for a split second and then dies. Good battery, new tensioner assembly and starter. Prior to not working, sometimes it would sound rough and choking when starting but a tap on the gas and it would stop (after fired-off) and run and idle fine. I have power at the alternator, the starter relay and relays and fuses are good (except no continuity on the EEC diode, dont know if it should have continuity anyway). When attempt to crank the battery voltage drops from 11.9 volts to 6.2 volts. Can you replace the voltage regulator or do i have to replace the alternator or is something else wrong??
  • I replaced the headlight switch and lights still come on. There are supposed to be two relays under the dash some where that one has to be bad but I can't locate them :confuse:
  • euphoniumeuphonium Great Northwest, West of the Cascades.Posts: 3,305
    Fuses under the dash and Relays are under the hood. Maybe near the coolant reservoir.
  • Has anyone had a PCM totaly shut down and take the data link with it.

    All fuzes and power check good even to the PCM and even the power to the ODB2, but no scanner will read and the car will not run.

    Starter spins it nicely but no run.

  • Has anyone had a PCM totaly shut down and take the data link with it.

    Was driving on I 10 doing 65MPH and blam.

    All fuses and power check good even to the PCM and even the power to the ODB2, but no scanner will read and the car will not run.

    Had to tow it home.

    Starter spins it nicely but no run.


    Sorry about double post the page numbers run backwards to most forums, most keep the first page #1 and the older post slip lower and on to page 2 and so on.
  • I am currently having problems with my 2004 Mercury Grand Marquis with the head lights not coming on or going out. All other light stay on. Turning the light switch on / off and it won't come on. Same symptoms in auto or manual Headlight mode. If I stop the car it will come back on. It then might go off after a while. I see others have had this same problem with the Ford but I have note seen any answers.

  • I have an 84 crown vic and my headlights would come on and I couldn't get them to go off. Ireplaced the headlight switch and didn't help. There was a relay under the radio behind the ashtray center of dash. I removed it and took care of the problem.
    My auto delay doesn't work but I can live without that. Also you might have a light sensor on top of dash by windshield that could be defective. Hope this helps. :)
  • The Lighting Control Processor had to be replaced. It is located inside the auto behind the glove box. If any one else has the problem they should tap on it to see if they can re-create the problem. That is how it was discovered. The problem might not appear when you want it too. It also might make the lights go back on when they go off. It is very costly but the headlights now work properly and do not go out any longer.

  • molarmomolarmo Posts: 1
    My "03 marquis has headlight issues. They go on automatically, but intermittently go off. When they go off, I'm unable to get them back on even if I turn the light switch on manually. When they do come back on I hear a "click". There seems to be no pattern..........very frustrating. Dealership is useless. Can anyone help?????
  • I have a 84 crown vic and my headlights would come on automatically also. I'm not familiar with 03 marquis but my problem was the auto lamp relay. I replace the headlight switch since it has a delay built in but didn't fix it. You also may have a sensor on top of your dash which detects sunlight and darkness which could have something to do with it.
  • markeezmarkeez Posts: 1
    I am having the same trouble with headlights they will go off whenever they want most of the time it is right when i use the turn signals. I was on the interstate for a while and they stayed on way longer than they normally do. Im wondering if it has to do with more draw with brake lights and signals. All though the past few days I cant keep them on for nothing. Just for kickers I put them on in the garage and just waited about 5 minutes and they went off and on and off. I unplugged one side of the headlights and it stayed on a long time so I tried the turn signal and it immediately went out. My wife had a fender bender a month ago so it has been hard to figure out why this is happening. I had to replace the header panel and grill. I guess I will have to try lcm. Where did you get yours. Thanx mark
  • I got the auto lamp relay from NAPA ($12.00) but it wouldn't work right so I just unplugged the relay and haven't had any problems, Your relay may be up front by the lights and the sensor also. Do you have a chasis electrical wiring schematic?
    That shows how your lights are wired with relays and such. I bought one off ebay for mine. I know it can get real frustrating. Hang in there. :sick:
  • tachyon54tachyon54 Posts: 1
    Lost my tail lights, brake lights, dash lights and turn signals a few weeks ago, replaced the headlight switch which fixed everything but the signals and brake lights. I've been all over it, replaced the flasher and fuses, still no luck. Strange thing is, the brake light in the back window works fine, just not the ones in the tail lights. I love my 94 Merc but this is driving me crazy. Anybody have advice?
  • pmitchellppmitchellp Posts: 19
    I have a 95 Mercury Grand Marquis and the headlights flash intermittently. I changed the headlight switch 3 times but it only solves the problem for a couple of months. :cry:
    Someone said something about an ambient light sensor in the rear view mirrror. Does my car have one of those, or anything like it? :confuse:
  • pmitchellppmitchellp Posts: 19
    I had a GMC Savana that had the same problem. It turned out to be a corroded parking light socket in front.
  • dowagdowag Posts: 2
    My dome light (and L/R floorboard lights come on and off at night and will drain the battery completely. Comes on for variable times and then is off for a variable time--only at night. I read where others have had similar problem but don't see that anyone has really had the problem fixed. This is a 2000 MGM. I have "sold" the car (will deliver in two weeks)....and now this problem. (otherwise a no problems car)
  • dowagdowag Posts: 2
    Thanks, I will check on the parking light socket. Would never have thought of that.
  • 2000 grand marquis, close doors, light goes out then 5 seconds later the light comes back on, 5 seconds goes off. this just started tonight. haven't had much time to play with it, but i will try all the ideas here. it doesn't happen when the car is running.
Sign In or Register to comment.