Hello, I'm in need of help diagnosing a charging problem on my '88 GTA. L98.

Original alternator went bad back in September. Now, I got another one which worked for a time, and then went bad. It was a reman, and considering it only lasted 3 months at most, I got another one free of charge. Put it in, charged up the battery, started it, it read 13.5-14.5 on the gauge, no flickering no nothing. So I let the car run with and without load. As I go to shut it off after letting it run for a bit, I find the volt meter is low, so check the car under load, lights flicker, etc.

Get the meter out, go on the battery. reads 12.7 at idle. 13.4-13.6 when given throttle. Same readings on the alternator battery terminal. Backprobe the connectors, and found the red one, reads 12.4 car off, 11.7 with key in on position, brown wire doesn't read anything at all except for a blip of 0.78, in on position, haven't tried it running yet. Somewhere I read, Pocket said there needs to be 12v on both those wires to have the car charging properly.

I also keep reading about the 3 wiring upgrades in some threads with alternator problems, what are people talking about here because I'm not finding any other info on what that is.

Did I get another bad reman? is the car frying the alternators? Don't have an Ammeter so I can't really check current. Battery is a couple years old but I am dubious that is the problem.

Thanks for the help.

EDIT: After typing this I went back out for more numbers and more probing. Brown, and white/brown wires still don't have any voltage. But things changed. This time, it started out ok, and over the course of 15 minutes under load the voltages dropped. Under load with lights on high beams etc etc, it would put out 13.2 dropping to 12.9 before I killed the load, but when revved, it went to a stable 14.3 volts on all three points, battery, 3 wire connector red wire, and battery terminal on the alternator. When load was killed it went to 14.0-14.1 volts. But every time I turned the lights on it would drop nearly instantly to 12.6-12.7. When lights were killed, it immediately went back to 14 volts. Again, measured on all three points.

 

Does it use an external voltage regulator or internal? I've never looked so i dont know

 

I ask because it sounds like when you have the headlights on the vr isn't seeing the drop at the battery therefore not sending more power the field coils. Check the alt. output at idle and then again with the lights on.

 

Sorry, I had the holidays then a wedding (my brother's) so I wasn't online much. Anyway, I had it tested, it was bad, got another one, this one worked, and still does, but when the lights are flipped on it drops from 14.3 to 12.7, not erratic like the previous one. I'm guessing its possible that despite charging up the battery, the charger may have not gotten it fully charged and it took out the regulator this time. Guess its back to the parts house.