Alternator taking a dump?

click · Jan 20, 2007

Alright so my car was driving fine parked it for less than 5 minutes and when it started right up but the battery light was on. So i went straight home and the battery tests at ~11.95 volts with the car off and ~11.56 with the car on and only changes a few hundredths when the engine is reved.

The when i test the alternators power wire if was jumping like crazy from ~3 to 7.5 volts.

I don't know of any other tests to narrow it down past it just being a bad alternator. Any input as to any other problems, stator, etc would be greatly appreciated.

Thanks.

Oh and the battery is a fairly new optima red top and the alternator as far as I know is "stock" cause it hasn't been changed since i bought the car in '04.

HISSIN50 · Jan 20, 2007

The battery should be in a decent state of charge before starting testing. However, it does sound as though you are running off of the battery .

The issue with the power wire should be addressed because the regulator's sense wire (labeled A, IIRC) is tied into that pathway. Ensure all connections are tight. If the sense wire is receiving bad input, the regulator doesn't act like it should (nor can it with a loose connection).

Parts stores can dynamically test the charging system, or you can take the alternator and/or battery in there and they can test them for you. The odds are good for the alternator but there are things to rule out first.

Good luck.

mo_dingo · Jan 21, 2007

HISSIN50 said:
The battery should be in a decent state of charge before starting testing. However, it does sound as though you are running off of the battery .

The issue with the power wire should be addressed because the regulator's sense wire (labeled A, IIRC) is tied into that pathway. Ensure all connections are tight. If the sense wire is receiving bad input, the regulator doesn't act like it should (nor can it with a loose connection).

Parts stores can dynamically test the charging system, or you can take the alternator and/or battery in there and they can test them for you. The odds are good for the alternator but there are things to rule out first.

Good luck.

QFTMFT!!!!!!

click · Jan 22, 2007

Alright i checked all the plugs/wires and cleaned them wire contact cleaner just incase, but still no charge. I guess it was just time for the alternator to stop working.

Thanks guys.

HISSIN50 · Jan 22, 2007

Do ensure the alt isnt putting out decent juice. I seem to recall a couple of folks lately with Optima issues (with almost new batteries). A bad battery can mimic the symptoms of a bad alternator. Just a quick check of the alt's charge stud with your DMM can be telling.

I still might have both the alt and battery bench tested as well. We have a good feeling that it's the alt, but it's always nice to *know* what the issue is, rather than making good guesses.

Good luck.

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