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Hello, I’m Matthew. I have a 1993 Nissan Stanza ALTIMA GXE with power windows, power door locks, cd/ cass radio, everything but a sun roof. I have replaced the alternator several times. In a month’s time, the alternator has gone bad and won’t charge the battery. The volts drop to 12.5 to 13.00 volts at idle, and my car’s brake and battery light comes on, I have a new alternator. My voltage is 13.64 volts at idle. My repair manual states voltage should be between 14 to 15 volts but not to exceed the listed volts, and if it’s lower or higher, there is problem within the alternator,
The question is the alternators I buy from the auto store are 80AMP alt’s, but I have seen in Texas that they sell 100 AMP for the same car. Are my AMPS too low for that car?

I live in Florida in Crescent City FL 32112.

How do I test for AMPs on an alternator?

An alternator should put out between 13.2 to 14.8 volts so your 13.64 is fine. If you are going through alternators like you say, then either you are getting badly built remans or you have another problem. I’m voting for another problem.

It could be wiring that is occasionally shorting out or a bad battery that has a cell with an intermittent internal short. BTW 80 amps is enough.

I agree with keith. Your alternator is fine. I would have the battery tested because it sounds like it might be on it’s last legs. Check and clean all the battery connections as well.

Have the battery tested, a weak, aged, or failing battery can kill an alternator in short order, regardless of rated output.

Look at it this way, your alternator is rated at 80 amps, but that’s peak output and can only be maintained for a short period. Can you run up a flight of stairs in 5 seconds? I’m sure you can. But how many continuous flights can you run, without a break, before you fall over?

A couple of comments. It is normal that your brake and battery dashboard lights come on when the alternator is dead or dying. I think the manufacturers do this in case one of the light bulbs (for the dashboard indicators) goes dead, you have a backup indicator showing you something is wrong and needs immediate att’n.

I’m assuming when you replace the alternator, both lights go out. That means it was a bad alternator you replaced, or something in the charging circuit anyway. There’s several possibilities. You could be just having bad luck with alternators. Or the belt could have come loose or not adjusted correctly. You could have a problem with another circuit taking power than it should. If you turn something on, like the headlights or AC, or the power windows, and notice the alternator light come on, that’s a clue the problem is in that circuit, likely a short.

I guess if it was me, once the new alternator was in, I’d keep an eye on the alt light. If I notice any correlation to when it came on to something I was doing, I’d make a note of it. And if it came on for no reason, the first thing I’d check is the belt tension. The next thing I’d do is probably change out the battery, as a test. Sometimes a bad battery will cause this.

Thank you all for the comments are helpful

the car starts better now, before it took a few cranks to start it, now its one crank.
I checked my volts again at idle was down to 13.20 volts, was at 13.98 when I started it up but slowly gone down, is this normal? I’m prob worrying like a mother hen. lol

the battery is new I got it back in Feb 2011, its a everstart, battery is from Wal Mart. can a new battery have a bad cell in it?

and yes my both lights are off they have not come on yet., but the volts are still very close to what the other Alternator had.

I guess expected to have alternator problems now car has 242200 miles on it.

well thank you again.

I also think what you have is a loose or corroded electrical contact.
Wiggle the connections to the alternator while a helper watches the dashboard for flickering lights.