Thread: Kind of a strange alternator/batterry issue?

Hopefully someone has some insight into this:

Yesterday I pulled out in my '97 200sx SE-R (w/ basic bolt-ons) and the brake light & battery lights came on the dash, which usually indicates a bad alternator. Other than that it ran fine for the few minutes I drove it but I went home and parked it afraid of being stranded.

I just started it up again, and as soon as I revved the engine past 5000rpms, both brake and battery lights dissapeared from the dash and the gauge lights shot back to full brightness. I shut the engine off and started it up again. The brake & battery lights were back on. I drove slowly out of the development under 10mph, then took it to redline and sure enough, both battery and brake lights dissapeared and the gauge cluster lights once again came back to full brightness.

I have all new belts, a battery that is 4 months old, but it's possible the alternator is the original, and there is 178k on the car. Also, I have the G-spec underdrive crank pulley which I installed a month ago (hence the new belts) but have had no problems with it.

So what do you guys think? Is the alternator on it's way out, and when the motor is revved high it temporarily works due to the higher load? The problem with this is that once the engine is revved high and the brake & battery lights go away, they stay off regardless of how the car is driven, but they come back on when you shut off and restart the motor. I never had this problem in any of my SR20's before. Thanks guys.

I had an alternator that would stop charging randomly, after building my alt harness just to rule that out... i returned the alty under warranty, and ive been fine since.

K here's an update for all of you absolutely riveted by this issue:

I had the battery & alternator tested at Autozone and both came up working good. Here's the other thing I noticed: when driving around and running the A/C, it varies in intensity randomly, ever so slightly. Also, I have had a CEL light since this I got the car, and I can see it dimming every so slightly in the gauge cluster at random times while driving, but it appears to stop and hold steady for a little while immediately after I revv the motor up to a high RPM and/or drive spiritly.

The belt is like 6 weeks old, looks good and is turning fine, the guy who checked the battery & alternator suggested there could be some sort of electrical drain on the battery and asked if I had a big amp and stereo, but I don't.

Could it be the G-spec crank pulley?

Did you test the alternator or Battery off the car?

The guy hooked up the multi-meter or whatever to the battery cable when the car was off, the battery came up good, then he had me start the engine and he said the alternator was good as well.

Forgive me, I know nothing about electrical stuff, only the motors themselves. I can do a cam swap in about 90 minutes in an SR20 but never changed an alternator.

Anytime I test and battery or alternator, I take them off the car and up to the auto parts store. They usually have the machine in house and OEM connectors to test alternators at Autozone as well. The issue with testing a battery after running it on the car for some time is that a good alternator doing it's job may fool those battery testers that the battery is good when it's actually not. After the car is cooled down for a few hours, take the battery off and back and do the same test. If you can manage to get the alternator off as well that would be best. Then go from there.

Even if the battery is less than a few months old do you think? I got it in May

Mine was only a few months old when it acted up, and it tested good on their machine inside the store when i returned it. I told them it wasnt and I didnt care that their machine said it was fine, I wanted another one. They gave me another one and I havent had a problem since.
Even though i rebuilt my alternator harness before i returned the alt, it needed it anyway.

Sounds like a grounding issue to me.

^This. What do your battery terminals look like?