2001 mercury grand Marquis the alternator light comes on and off.just put in brand new one still doing the same thing

Asked by Apr 21, 2015 at 04:00 PM about the 2001 Mercury Grand Marquis LS

Question type: Maintenance & Repair

4 Answers


When installing a new alternator. You MUST first disconnect the battery or you can fry a brand new alternator in the first 30 seconds of the car running. If you didn't disconnect the battery first, you might need another alternator. Take it off and take it back to the parts store that you bought it from and ask them to check it for you to see if the diodes are fried. If it's OK then you have another problem. Check the tension on the belt and check if it's worn. That could be your problem, also check for loose or bad connections on the Alternator plug or wiring. Check your battery terminals also for loose or corroded connections. Good Luck, Kenny / MrBlueOval


Everything Mr Blue says is right on, Those belt tensioners go bad and should be replaced when the belt is replaced, but not always done. I'd replace them both, just for good measure.


One more thing I forgot to mention. I'll assume that your battery isn't completely dead but I'll address this issue incase others are reading this for help with their vehicle as well. A new alternator won't recharge a dead battery so if your (or anyone else's) alternator goes out completely and your battery goes dead, you need to recharge the battery first or you will also FRY your alternator in a few seconds (not in minutes) after starting the car with a jumpstart. Jumpstarting a car with a dead battery can ALSO FRY an alternator too. Jumpstarting should ONLY be done in an emergency when you are stranded in harms way. If you have access to a battery charger, do that first. An alternator (brand new or ten years old) will FRY it's diodes trying to recharge a DEAD battery so make sure your battery is FULLY CHARGED before trying to jumpstart a car. I just thought I would throw that in for others reading this post. Kenny / MrBlueOval


Obviously you won't need a jumpstart if you have a fully charged battery but I was trying to say to charge up the battery with a charger if you can first "instead" of jumpstarting. I'm Sorry if I didn't word that correctly the first time for those who didn't understand what I was trying to say. Kenny / MrBlueoval

Your Answer

Grand Marquis

Looking for a Used Grand Marquis in your area?

CarGurus has 1,268 nationwide Grand Marquis listings starting at $1,900.


Mercury Grand Marquis Experts

  • #1
    Tracy Hooks
  • #2
  • #3
View All

Related Models For Sale

Used Lincoln Town Car
22 Great Deals out of 1,456 listings starting at $1,850
Used Ford Crown Victoria
940 listings starting at $1,999
Used Chevrolet Impala
395 Great Deals out of 27,759 listings starting at $1,499
Used Ford F-150
2,602 Great Deals out of 221,772 listings starting at $1,222
Used Ford Mustang
326 Great Deals out of 38,826 listings starting at $1,995
Used Chevrolet Tahoe
659 Great Deals out of 38,085 listings starting at $995
Used Honda Accord
607 Great Deals out of 92,577 listings starting at $1,495
Used Cadillac DeVille
1,258 listings starting at $2,700
Used Chevrolet Silverado 1500
2,255 Great Deals out of 152,112 listings starting at $1,499

Used Cars For Sale

2010 Mercury Grand Marquis LS For Sale
3 Great Deals out of 63 listings starting at $3,500
2009 Mercury Grand Marquis LS For Sale
3 Great Deals out of 70 listings starting at $3,400
2008 Mercury Grand Marquis LS For Sale
71 listings starting at $3,400

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.