rocketman4321

In the last day or so, 2-3 times the battery light (right side, by the "BRAKE" indicator, not the LCD warning display) has come on right when starting the car. Voltmeter also stays low. If I rev the car a little, the light goes off and the voltmeter reads normal, ~14V. Serp belt appears healthy and tensioned. I've not yet been able to check if the alternator pulley is turning when it does this, but obviously it is after rev'ing.

I'd previously seen some slight variations in voltage, cleaned cables, etc., but wasn't going to tear the car apart over the winter. It was either fine, or would degrade slightly when warm--a bit above the "14" line when cold, and maybe on or just below it in warmer temps or with the car warmed up. (Past testing with a good DVM indicates the dash voltmeter is pretty accurate, if hard to read precisely.)

Alternator? Car's at 112k, and the original failed in 2009 at 67k. This one's a rebuilt unit, but are these really just 60k units with awful access to repair? Timing belt's up-to-date, so the surgery would be just for the alternator.

johnkk

Sounds like voltage regulator has lost a few diodes, but still has a few working. Could be alternator though. Depends on what was "rebuilt" on your replacement. The brushes on the regulators normally wear out at about 150k-175k miles, but the diodes can fail randomly.

rocketman4321

At one point in the earlier troubleshooting I put a 'scope on it and didn't see and missing phases in the waveform, but of course that could've been at a time when it was working.

Are the regulators available separately, and does it include the brush assembly? Unfortunately, still the service position to fix. I've also thought that the cable could be loose or failing, but can't get at the connection on the back of the alternator without, yes, going to the service position.

Of course today, two starts and 10-mile drives, no indicator and the voltage was just above the 14 V line the whole time.

tester123

Just a thought: Did you check the cables/bolts/nuts tight at the alternator and battery?

johnkk

With any luck it's a bad connection. That said, since you have to assume the position, I would put in a new regulator, just cuz. It does include new brushes and not too $$.

Kombi03

Did you ever find the problem?