(G) Generator (Alternator) light comes ON (and stays on) when car is OFF

DARKNES · 04-04-2008, 03:11 PM

Ok, Here's a weird one, for me anyway.
When I shut the car off, the (G) light lights, and stays on.
Guy at the local shop says possibly diodes, or voltage reg., but someone else may have been through this and have a definitive answer.

I did search the forums to see if anyone else has had this problem, but didn't find anything, so forgive me and point me in the right direction if this is a rehash.

Thanks!

-Thomas
'78 911SC

RoninLB · 04-04-2008, 04:16 PM

http://www.pelicanparts.com/914/914qa/914Q_electrical_alternator.htm

DARKNES · 04-04-2008, 04:29 PM

Thanks! I just *knew* I had too much time and money this weekend. ;-)

rlane · 09-06-2008, 03:50 PM

My alternator light is staying on ONLY when the key is off, it is not on when the car is running. I had the engine out for some oil seal repairs this summer and it was not doing this before. Is the thread refernced above still true and I suddenly have a bad alternator?? Could it be that I wired something up wrong?

DARKNES · 09-06-2008, 06:53 PM

Yes, still true. Yes, you could have a bad alt. Yes, it might be wired up wrong.
My problems were preceded by me buying a BMW (alt went out the DAY I brought the Bimmer home,) which made the Porsche jealous, so in retaliation for my Bavarian infidelity to the best the stud farm has to offer, she forced me to buy her a new alternator (and I don't even LIKE BMWs! It's for my fiancee! The thing's like... a less reliable Toyota Camry, with a German accent!)
In your case, I'd pull it and test it. But then, I altered the wiring harness to include a 3-pronged male/female plug, making getting it in and out a lot easier. (Thanks McMaster-Carr!)

timc · 09-06-2008, 06:57 PM

Bad diode in alt.

47silver · 47silver's Garage

the external has 4 connecton points on the alternator
2 reds go to b+
black goes to df
2-browns go to d-
blue goes to b61

internal
2 reds to to b+
2-brown to d-
blue to b61

black is not connected.

check the wiring..
i
if not then diodes are bad

rlane · 09-07-2008, 05:29 AM

Thanks guys, my geuss is that I wired it up wrong, will pull it this afternoon...not one of my fAVORITE JOBS BUT CLEARLY HAS TO BE DONE

rlane · 09-08-2008, 05:59 AM

OK, wiring looks good except only 1 brown wire to D- (THIS IS THE 73 rs CLONE. iT DID NOT HAVE A GROUND STRAP TO ENGINE BLOCK CONNECTION ON THE ALTERNATOR (BASED N PICS i SHOT AT TEARDOWN. sHOULD i ADD ONE? (DARN CAPS)

timc · 06:04 AM

yes, should go from one of the 8mm nuts (IIRC) that hold the back alt air distribution cover on to one of the 13mm case nuts.