I need a little help.

Car: 93 geo prizm lsi 1.6l (don't laugh, it was free)

Story: I was on my way home from Atlanta on 40 close to raleigh when I got stuck in a bunch of traffic due to the construction. After sitting still for a while, I noticed that my battery light was on. I replaced the alternator about 3 years ago because the battery light came on and Autozone tested the alternator and said it was bad. The light stayed on until I got through all the traffic and back up to highway speeds, then went out. Didn't have any trouble with it the rest of the trip. Now that I'm back in raleigh I've messed around with it a bit, and have found that any time it stays at low speed (~20 or less) the light will come on, but go out once appropriate speeds are again reached. Also, it makes a whiney sort of noise after the car is up to temperature. The belt is tensioned to the specs in the haynes manual. I also removed the belt and spun the alternator by hand, it seems to turn freely (doesn't seem like the bearings are bad). I took the car to Advance today, and their testing machine said the alternator was fine, but something tells me it isn't.

Anyone have any idea what the issue could be here? Could it be that something is overstraining the alternator? I do have a cd player and ipod adapter, but no subs or anything like that that would put extreme draw on the alternator. Even with the stereo off, at idle for several minutes, the battery light will still come on. My first instinct was to just replace the alternator again, but my dad said that alternators sometimes make noise if over strained, and it would suck to be down 100 bucks and still have a problem.

Battery is also only 3 months old.

Sorry that's kind of long, but if anyone has any suggestions i'd be very appreciative.

11/20/2006 5:34:58 PM

You need to yank the alternator and test it on a test bench. I've got a feeling that your rectifier might have shit the bed.

11/20/2006 5:42:37 PM

Where might I find a test bench? Trying to avoid mechanics if at all possible. I'll google the rectifier and see if i can come up with some symptoms that sound similar....

11/20/2006 5:46:53 PM

Advance Auto has a test bench.

The on-car tests can't do but so much, and I'd rather try to isolate the issue. Hence the alternator ALONE on the test bench.

11/20/2006 5:50:34 PM