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

6,325

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

1,205

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.

6,325

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

6,325

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

Add photo

Related Questions

Grand Marquis

Looking for a Used Grand Marquis in your area?

CarGurus has 1,828 nationwide Grand Marquis listings starting at $500.

ZIP:

Search Mercury Grand Marquis Questions

Mercury Grand Marquis Experts

#1 Tracy Hooks
Tracy Hooks
Reputation 5,260
#2 kbro
kbro
Reputation 2,050
#3 Js08016
Js08016
Reputation 1,660
View All

Related Models For Sale

Used Ford Crown Victoria
9 Great Deals out of 982 listings starting at $2,990
Used Lincoln Town Car
26 Great Deals out of 1,827 listings starting at $1,695
Used Chevrolet Impala
593 Great Deals out of 29,263 listings starting at $1,300
Used Ford Taurus
192 Great Deals out of 19,379 listings starting at $500
Used Chevrolet Tahoe
632 Great Deals out of 27,862 listings starting at $600
Used Cadillac DeVille
7 Great Deals out of 1,610 listings starting at $2,000
Used Honda Accord
716 Great Deals out of 82,605 listings starting at $500
Used Ford Mustang
306 Great Deals out of 45,682 listings starting at $2,200
Used Ford F-150
2,420 Great Deals out of 210,948 listings starting at $895

Used Cars For Sale

2010 Mercury Grand Marquis LS For Sale
5 Great Deals out of 91 listings starting at $4,100
2009 Mercury Grand Marquis LS For Sale
83 listings starting at $4,995
2008 Mercury Grand Marquis LS For Sale
4 Great Deals out of 97 listings starting at $500