Br3nn4n

Hi guys,

Hopefully I can get some insight on this issue. Took a long drive to LA and back about a week ago (OK, not THAT long but I always worry when driving this car in areas such as Compton). Took 2 hours in traffic coming back, and when I got off at the exit I noticed the ! indicator light flickering on, along with the voltage gauge around 10 volts.

I kept the voltage up enough to keep the car running, by keeping the gas held down a little. This, in turn, caused my fans to come on when it would get too hot, which would only worsen the problem of low voltage.

So, after buying a battery charger I made it home and the car died while parking. Fwew! Charged the battery, car starts right up but nothing from alternator.

Did a lot if reading, learned about the light for the exciter circuit. Also, the self excitation when you rev it high enough, which works when it is completely cold.

Seems like my alternator stops working after the engine gets hot. The light does not come on, but I know it works because once the alternator stops outputting it will flicker on as the battery gets a little low.

So - car runs fine. Starts up immediately with charged battery. Cold - no dash light, but I can self excite the alternator through revving to 4500 RPM, and it works for roughly 15 mins. Engine hot - no dash light, CANNOT self excite the alternator through high rev.

What should I check? This only happened after the long drive. Before that drive, I'd always had a solid horizontal volt gauge while driving, right in the middle of the range.

What I don't get is why it suddenly stops working after running for a while. Thoughts?

I also just today noticed a humming noise, coming from down towards the ECU, in the passenger foot well. I can hear it with the key in the ON position.

Here's a video for ya (shot in 4K resolution, watch it on your new TV!).


Thank you guys for your help!

Br3nn4n

Any ideas, guys?

Tiger03447

I know it's a pain, but take the Alternator off the car, take it to AutoZone, have them put it on their test bench...It will check the diodes, rectifier, and voltage regulator circuits...it's a free service. They can also see what the voltage output is..should be between 13.5 to 15.5 volts. It will give you what the normal limits are and where your alternator stacks up..Could also be brushes...might be able to get a regulator/brush set for it and repair it yourself.. If it's a bearing going south, they have no way to check it...They can also price one out to you with a lifetime warranty...jus sayin hope this helps some..Merry Christmas...

Br3nn4n

Alrighty, thanks. It's really not that hard of a job, correct? Will having them test it will rule out a bad alternator, absolutely? Merry Christmas to you as well! I got a short shifter for the 944 so now I actually feel like working on this car again.