battery light on at idle...goes out with higher revs
 

does this mean the alternator is starting to fail? i have a new optima red battery and just had a new voltage regulator installed.

thx

Tighten your belt maybe? (fan belt, not the one on your pants).

Todd

Check your battery voltage with an ohmeter... it should read over 14 volts,even at idle !

that's how mine let me know it was done.

I would suspect bad diodes in the alternator.

+1

great...i just had the alternator out in the rebuild shop... the only thing replaced at that point was the voltage regulator. i guess the rebuilder missed the other. ill check with the voltmeter.

thanks for all the replies.

My '72 911E has been doing that for five years now. I haven't seen anything change...

Vic

Depending on the year of the car, alternator brand/type... it could be normal. I recall my 356 doing that all the time - perfectly normal; however not to normal on a 911, based on what you've doen already, check the alternator.

Mine has done that for over 10 years... At idle, I get 14+volts at the battery, but the light is bright. I remember reading something about changing the resistance on the bulb when moving to a different style of voltage regulator. This was in a Porsche Factory bulletin. I figured I'd just ignore it for now... that was 10 years ago ;)

-Michael