Mechanics

NEW BATTERY WON'T HOLD A CHARGE.

1995 Pontiac Sunfire

Electrical problem
1995 Pontiac Sunfire 6 cyl Front Wheel Drive 150000 miles

My car battery won't hold a charge, I replaced the battery and had the repair shop test the alternator and it test good, So now what? The battery connections are brand new.
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Srivera0623
March 11, 2010.



Hi, was the alternator, checked on or off the vehicle? Did the shop test for a battery drain?

JDL
Mar 11, 2010.
I took it off and had it tested in a parts store, How would they test for a battery drain?

Tiny
Srivera0623
Mar 11, 2010.
If the problem was the wiring circuit to or from the alternator, that won't show up, testing alternator in store. The alternator itself, may be fine. The charging system needs to be checked on the vehicle.

To check for battery drain, you can check for excessive amp draw, everything turned off. Usually around.030 is normal, no where close to half amp. I don't have the exact spec in front of me. If the drain is excessive, you can pull fuses, one at a time, when you pull the fuse on the affected circuit, the drain will drop to normal. Check for any lites that may stay on, best time to check is in the dark. Ash-tray--glove-box--interior--under the hood-- in the trunk.

An older way to check for battery drain, is to take battery cable loose, use a testlite between end of cable and battery post, if the lite stays on, there is a drain. Then you do the same thing with fuses, one at a time. I think it is best to check amp draw.

JDL
Mar 11, 2010.
I can drive it for about a half hour and then the battery slowly starts to drain, blinkers start to blink slower, I thought for sure the battery was bad because it wouldn't stay charged.

Tiny
Srivera0623
Mar 11, 2010.
With the vehicle running, it should be the alternator carrying the load, not the battery. If something is wrong with the charging system, it will start taking it from the battery. The way your talking, I'd have to check the charging system on the vehicle. If you have a digital multimeter, and want to do testing, I can tell you how to start?

JDL
Mar 11, 2010.
Yes, I have a multimeter, and would love to do the testing myself. So please tell me how to start. Thanks Shannon

Tiny
Srivera0623
Mar 11, 2010.
With vehicle and everything turned off, place meter leads across battery posts, take a reading. The generic spec for a fully charged battery is around 12.6 volts. If the battery is run down, take it off and get it charged.

Then start the vehicle, take a second reading across the battery posts, the second reading should be higher than the first, if the charging system is working.

JDL
Mar 12, 2010.
Hi, ok the battery read 12.4V before it was started, then I started it and it read 11.9V. So when you say charging system, what do you mean?

Tiny
Srivera0623
Mar 12, 2010.
It looks like the alternator isn't charging. Maybe a problem with the wiring circuits to or from the alternator? Do the same test at the alternator bat terminal. Engine off and engine running. Don't get the leads caught in anything. Use a metal part of engine for meter ground. If the second reading, engine running, is higher, there is a problem with the wiring circuit from alternator to battery. If the second reading still isn't higher than the first, you need to check wiring circuit to alternator. I know you said the alternator was good, right?

JDL
Mar 12, 2010.
Yes, the alternator was tested and they said it was good. The voltage at the alternator was 12.1 with it on and off.

Tiny
Srivera0623
Mar 12, 2010.
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