Batt/Alt Warning light on 81 308GTSi

This is fairly typical / normal on that car. My '81 does it all the time --- always has --- even after fresh alternator / belt services. I wouldn't worry about it --- unless it gets worse (longer time elapse).

This I haven't seen before. I wonder if the alternator may be getting a bit heat-soaked??? I would check to make sure the heat shields are in place and in good condition.

I would also double-check the alt belt condition and tension. These symptoms could also be early signs of the alt going south ---- but, I wouldn't worry about that either, until (if) it fully goes.

 

The heat relationship is strange but clearly the alternator/regulator is kerplunkt. Later cars have a diode in series with the warning light to prevent the bad regulator diode from draining the battery when the key is off.

Alternators are 3 phase devices with numerous diodes to convert the ac voltage to dc for the battery. Failure of a single diode only kills one of the phases and some charging is still possible. But not for long.

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Ferraris - don't ya just luv 'em?

 

My vote for what it's worth: at the very least an alternator rebuild is in your future.

 

Not really ---- unless the battery is intermittently shorting to ground somewhere or has a mechanical defect (e.g., bad / loose post, broken internals, or a crack in the case). It really sounds like an alternator problem. Since you are the original owner, when was the last time the alt was replaced / rebuilt?

I can tell you also that my car did not start showing this quirk until it racked up about 40K miles (I bought it with 27K and it now has 85K). When the entire electrical systems of these cars start to get "old" they get more and more quirky as resistances build and contacts wear here and there.

 

+1

 

Age, not mileage can cause problems. Have your charging system checked out with an ARBST.