Battery light comes on, but checks OK ?

[JohnW63]

It has rained a LOT here in California, so keep that in mind with this post.

Three or so days ago, my battery light would come on a very low RMPs but fade off as the RMPs rose to 1500 and remain off, until they came back down. It was consistant for two days. I have run through lots of puddles so I was hoping for just water in the wrong places. Last night, even though it is STILL wet all over the roads, the light stopped coming on. I could be wrong, but I thought I smelled burnt electronics for a few minutes, while I was driving, but it could have been something outside the car. ( Yes , I checked. The light still works when you turn the key on. ) I borrowed a handheld tester from the mechanics at work, and the darn thing checked out OK ! I rather doubt the alternator healed its self. Any ideas ? As far as I know, this is the original alternator in a 95 SHO with 130,000+ miles.

 

[Slo-Sho]

3.0 or 3.2 alternator?
What was the voltage when you checked it?

 

[JohnW63]

3.2 motor.

I think with the key off, the battery showed in the 12.5 range and with the car running it was in the 13.5v range. The tester had me rev the motor up for 5 seconds for the first test and then put a load on the system, so I turned the lights and heater on.

Of course once the light started comming on, a few days ago, I started wondering if the alternator was making the same amount of noise that it always did. It might be a bit lounder. Maybe.

 

[Slo-Sho]

A common problem is the 3 wire connector that goes into the alt. The wires/terminals become loose. Try wiggling that connector to see if you can reproduce the symptoms.

 

[sdpatt]

Another common problem, usually with higher mileage alternators, is that the brushes wear down and don't make good contact to allow sufficient charging current to flow at lower rpms. Your light will probably be back until you resolve the alternator situation. Keep this in mind.

 

[JohnW63]

So, even though the light is off now, I can expect it to come on at anytime ? Since the 3 wire plug points up, I was wondering if it could have gotten water in it that took awhile to evaporate.

I've heard that you need to get an alternator with noise supression for these cars. Is that true ?

 

[30footSHO]

I recommend taking out the alt. and having it rebuilt. If you're a savvy guy, you can do it yourself. My alternator in the '91 was actually having problems at higher RPMs, even after the rebuild.