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I own a 99 MGM and the battery light comes on intermittently. It does not stay on. I was told that I may need a new battery. Well it is 6 years old and is orginal equipment. I replaced it today and the light still comes on from time to time. the charging guage doesnot show any problems. I do not notice amy problems with the car. No trouble starting even on really cold mornings. Has anyone had this problem before and if yes how did you fix it?


thanks Arthur [img]smileys/smiley19.gif[/img]

 

Hi, Arthur.
I've never had the battery light come on before on any car I've owned (likely because my cars never had one) but my first inclination would be to check the alternator, the belt and the belt tensioner. Before I got my current car (a 2003 Mercury Grand Marquis)I had a Corolla on which the belt tensioner broke (it broke its seal and leaked its hydraulic fluid). This caused the belt to be damaged, which then caused the altenator to be damaged and finally the battery of course was damaged as well. That's when I learned the altenator is a wicked and deceptive device. According to theservicing mechanic at the dealer (who happens to be a friend), the altenator willappear to befineand charging properly at first, but if you stay with it and keep it running while testing, it will eventually show that it only occasionally breaks up the charging process.That may very well explain why the light comes on only intermittently and it's not on constantly. Is it possible that light's coming on only at those moments when the altenator is not charging?? It couldn't hurt to check it out.Edited by: AngelD

 

If you own a multimeter,simply check the dc voltage at the battery before you start the car.This will give you a base number to start with. A good battery should be between 12 vdc and 12.9 vdc.


Start the car and check again. The number should be between 13.4vdc to 14.3 vdc.


If thisIS the case,the alternator output is fine, I would check serpentine belt(as mentioned in above post),if it is NOT the case,a replacement alternator is the ticket.

 

Hey thanks guys, Lenny and AngelD,


I have a multimeter and I am an electrician. I will try testing the voltage and re-checking the belt. I will let you know wwhat I found soon.

 

Hello, Lenny and VaDancer,
Is it possible to keep the multimeter connected and have the car idle for a certain period of time? If it is possible, then that's what I was suggesting, that the multimeter will eventually show adrop.
Good luck VaDancer! Lenny, thank you once again. You've helped me in the past andit's very much appreciated.
Edited by: AngelD

 

Yes it is possible. You can either use alligator clips(if test leads allow) or put the leads into the terminal post brackets and leave then in there the whole time.I do this alot,instead of using a battery load tester( I dont trust them) because a digital meter gives a more accurate reading.

 

Thank you, Lenny.Edited by: AngelD

 

Hello again guys, Have not found out what is causing the battery light to come on yet. Voltage readings at battery with car not running is 12.6 volts. With car running, voltage is 14.9 volts. Have not been able to catch the light on and stop to check the voltage at that time. Had Auto Zone check the alternator and they say it is normal and OK. Real puzzler to me. Nothing on the car seems to trigger the light comming on. So what ever it is, it has to be something that is not turned on by me while driving. Just running the car in the driveway will not usually get the light to come on. It only happens when I drive it. We went away on a trip last weekend and on the 250 mile trip there it only came on once for about 3 seconds. But on the trip back it came on about 5 min after we got under way and stayed on the entire trip. It even came back on right away after we stopped for gas. Got home and went to get the meter and my wife had cut the car off. Restarted and the light would not come back on. JUST MY LUCK! I think I just might install aditional wires from the battery and connect them to my meter in the front seat and just drive around to see what measurment I can record.

 

Awesome idea with having the meter connected at all times, VaDancer. Why are electrical issues always so difficult on cars, anyways? Seems everything is pretty straightforward except the infernal wiring.....and please don't think it's your luck, it happens to everyone. I cannot count the number of times I've taken the car to a mechanic to have him check out a noise that's on all the timebut magically silences itself when the mechanicis within a 20 foot radius of thecar. It's just Mr. Murphy up to his usual pranks. Keep us posted, please. I'm very curious and the info might help me (or others) one day ifour battery light should ever come on.[img]smileys/smiley1.gif[/img]

 

maybe its the pesky little voltage regulator. 14.9 volts seems like it might be high enough to trigger the dummy light. let us know! ( it probably has an internal regulator )