Battery or Alternator? [Archive] - Forum


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08-03-2004, 07:21 AM
This morning my 99 GAGT wouldn't start. No cranking at all---1 click and nothing. Jump started it and drove to work 45 minutes. Shut the car off and tried to restart and nothing---only 1 click.

No dash lights came on during driving.

AC Delco "green eye" battery is still the same green color it's always been.

Any way to tell if it's the battery or alternator?

08-03-2004, 07:36 AM
AutoZone is suppose to test alternators for you for free.

08-03-2004, 07:39 AM
That little green eye thing on the battery is completely useless. Seriously it's extremely inaccurate and I would not use that to decided whether or not the battery is ok.

Because you were able to drive to work for 45 minutes without having the car die out I would probably say you just need a new battery. However, you can take it to a Sears Auto Center or similar shop and have your electrical system tested for around $10.

If you do have the original battery in there then it's more than likely time to replace it.

11-29-2004, 02:39 PM
I had a dead battery boosted and burned out the alternator as it was tring to charge a dead battery!!! Happened before I could make to garage. Slightly P.O. as I had to replace both 6weeks after buying the car. BUT it was a CHEV.. Boost once and hurry like hell to have it replaced

11-29-2004, 03:46 PM
The fact that you were able to jump it and it ran for 45 minutes tells me that your battery isn't holding the charge from the alternator. If I'm wrong on this, someone correct me please.

11-29-2004, 04:42 PM
Are you sure that there isn't a light on or anything...say...glovebox isn't shutting all of the way. I know my 2001 turns the circuit off if I leave the interior lights on, but are you sure that you don't have an open circuit somewhere??

Just my $.02

11-30-2004, 01:26 PM
Throw a meter on the battery when the car is running, should be 13-15 volts if the alternator is working. If that voltage looks good and you shut the car off and it drops to anything below say 10V after driving 45min it's the battery. Other, less likely things, such as bad engine ground straps or loose alternator wire to the battery can also cause this, but based solely on your description my money is on the battery. Either way I'd check it out before replacing anything.

The "green eye" just tells you the specific gravity of the water/acid in the battery, they don't always work the greatest and should really be used as a reference only.