Battery light flickering on 2001 Toyota Corolla

Two days ago, my battery light came on while driving. The positive pole had some corrosion, so we cleaned that off, and checked all the other connections, light went off, and everything was fine. Yesterday, the light began to flicker. It will stay on for 2-15 seconds at times, but mostly just flickers, and at random intervals. We pulled the alternator and had it tested, and it tested better than fine. The belt and cables are in good shape, but the light still randomly flickers. The dash and headlights are not dimming at all, and the car has no problems starting or idling. Right now, the mechanic thinks that it could be a sensor or loose wire in the warning system, and has nothing to do with the alternator or battery, that my battery is still receiving charge from the alternator, but we have to wait until the light comes on and stays on to hook it up to the computer. I was wondering if anyone has any experience with this problem or any other ideas.

by in Mount Pleasant, MI on April 30, 2009
1 answer 1 comment
ANSWER by on April 30, 2009
I have seen this type of problem before with Toyota Alternators. We check them on an old Sun scope where we can look at the diode pattern ,alternator out put charge rate and voltage. When the battery light next comes on and stays on, pull over to where it is safe. With the engine running hand brake applied, get a friend to watch the battery light, hit the alternator itself with moderate force (not a sledge hammer) does the light go off, if so the brushes, regulator, diodes or some other internal problem is present in the alternator itself. Often with the car hooked up on our tester I can hit the alternator get the diode and charge pattern to go away, tap the alternator again and get it to come back and charge normally. If the charge light is on the battery is not being charged so you will not be able to drive far , but if by tapping the alternator the light goes out the problem is in the alternator.
COMMENT by on May 08, 2009
Autotechpat, thanks for the advice. When I took the alternator in to my guy, he actually pulled the entire thing apart after testing it and the entire thing was clean, brushes, regulator, diodes, ect.
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