New alternator, but battery gauge still low

Karmine Ciotoli

Asked by Mar 06, 2015 at 08:54 PM about the 1999 Mercury Grand Marquis 4 Dr LS Sedan

Question type: Maintenance & Repair

I got a used 1999 Mercury Grand Marquis a few weeks ago.  Theres about 106,000 miles on it so far and I noticed the battery gauge needle was starting to drop and not stay in the middle like it's supposed to.  I went to Autozone and had a test done and they said it was the alternator, so I had the alternator replaced at an auto repair shop but the needle is still running low.  I then went to another Auto place for another battery testing and they said it tested as a good battery so what could be the issue??

5 Answers

Karmine Ciotoli

Here's the new alternator btw-

3 out of 3 people think this is helpful.

Take it to the auto parts store, they can test the battery and alternator output with the same tool also check all connections on alt.. Start with that.

2 out of 2 people think this is helpful.
Douglas Wyczalek

If you have a VOM (volt ohm meter) you can check it yourself with engine running VOM positive to

1 out of 1 people think this is helpful.
Douglas Wyczalek

Postive lead of VOM to positive lead of battery and negative lead of VOM to negative lead of battery it should be 14.5 volts if it is I say it was your gauge in dash.

Kristina Williamson

I just had the same issues with my 95 mercury grand marquis. I bought a new battery and alternator and the same thing. Battery light still showed up as low. I had O'Riellys test both battery and alternator and they showed a good reading. My alternator has 3 electrical outlets on it. The main plug to it, the hook wire you screw on and a tiny plug between them. I was told the wiring harness is notorious for going bad. It's a dealer item only. But it doesn't have the small plug on it. So, I rewired the new one I got from the dealership and bought some small wire adapters at O'Reillys and rewired the small plug. And still had the same problem. I took it to a mechanic shop, asked him to find the problem, and the alternator was faulty. It wouldn't keep a charge. So I exchanged put it on the car, and it is doing great. So, I'd get the alternator tested somewhere else. And if it's good, try the harness and plug. Good luck! It was super frustrating!

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