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Alternator light on but charging ok

Alan Bowler

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It's an odd one.

Old alternator packed up, warning light came on, no sign of charging, battery voltage didn't I crease with RPM.

I sent Alan an alternator to try. It came off an engine that came to me for a rebuild. No reason to suspect it but not tested, as I said to Alan.

It seems to charge absolutely fine, 14.5V but the warning light is on bright and solidly. Not dimly like a failed diode might show. I talked Alan through checking the wiring, the warning light comes on when you short the brown and yellow wire to ground (ignition on, engine off) and goes out when disconnected, suggesting the circuit is all OK beyond the alternator.

I can only think that there's a problem with the regulator pack on the back of this alternator :(

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I had a very similar problem.

Original alternator packed up and I had it repaired, it all tested OK on the test rig he used. The alternator charged fine but the warning light stayed on when I fitted it. I took the repaired alternator back to the repairer and he replaced some additional slightly worn parts, but the result was the same - charging, but light on. There was also a discernable high pitched whine from the alternator when the ignition was on, and a constant drain on the battery even with ignition off.

I also got a replacement alternator (excellent service Revilla *thumb_up*) and that was fine, confirming that there was nothing wrong with the wiring.

Took the original alternator back to the repairer again and he replaced the regulator pack - again - and now it works fine. Looks like you just can't rely on new components to work properly!!


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