Is my alternator done for?

Its a new 95A alternator, installed 3 months ago. So i'm making a 6 hour trip from Maine to MA and all of a sudden my subs start cutting out, i look at the volts and they were spiking up to 16 or 17 volts!!! "I unplugged my subs just to be safe." If i kept the RPMs below around 1900, the volts wouldn't spike, i drove the car like this all the way and luckily she made it. But when the volts arent going crazy, its still overcharging at idle around 14.5 volts. I just don't understand this, they reallly mustn't build em like they use to because i put a lot of stress on my stock 78A alt with my stereo system and never had a problem.

Sounds like the voltage regulator went bye-bye. I remember this happened to me once about 4 years ago, and I was sure I was going to burn out the headlights on my way home from my friend's house ... couldn't understand why they were so bright, looked down at the volt gauge and it was on 18!

Is it a Delphi alternator or aftermarket?

Its a new 95A alternator, installed 3 months ago. So i'm making a 6 hour trip from Maine to MA and all of a sudden my subs start cutting out, i look at the volts and they were spiking up to 16 or 17 volts!!! "I unplugged my subs just to be safe." If i kept the RPMs below around 1900, the volts wouldn't spike, i drove the car like this all the way and luckily she made it. But when the volts arent going crazy, its still overcharging at idle around 14.5 volts. I just don't understand this, they reallly mustn't build em like they use to because i put a lot of stress on my stock 78A alt with my stereo system and never had a problem.

I think I mentioned this to you before. these low amp alternators will not last with high powered noise makers. the current surges will destory the rectifiers. try to locate a larger alternator with an external rectifier mount on the alternator. this will last longer. you do have the large capacitor at the amp input I believe .

On my 85 I usually read anywhere from 13.5 volts to 14.8 volts. Unless if I'm mistaken, 14.5 volts is normal -- although I don't know if that's bad for the stereo system/subs. I have the 78amp alt. Had a 95amp before and same voltage if I recall correctly.

Just my :2cents:

On my 85 I usually read anywhere from 13.5 volts to 14.8 volts. Unless if I'm mistaken, 14.5 volts is normal -- although I don't know if that's bad for the stereo system/subs. I have the 78amp alt. Had a 95amp before and same voltage if I recall correctly.

Just my :2cents:

your correct that this is in the normal range 13.5-14.8 volts under normal operation.

if your using more than 70-90amps this voltage will drop below 13.5volts.
if the regulator fails this would go to 18volts. this would then damage the battery plates and may on a newer vehicle damage the PCM.

When you guys talk voltage are you talking multimeter readings or factory gauge??? Factory gauges should NOT be trusted for a number but rather watched for a change from normal.


You know on the later b-bodies a 135amp alternator was common so there might even be a factory higher amp solution out there.

When you guys talk voltage are you talking multimeter readings or factory gauge??? Factory gauges should NOT be trusted for a number but rather watched for a change from normal.


You know on the later b-bodies a 135amp alternator was common so there might even be a factory higher amp solution out there.

I'm using an aftermarket gauge so the readings are fairly precise.

I think I mentioned this to you before. these low amp alternators will not last with high powered noise makers. the current surges will destory the rectifiers. try to locate a larger alternator with an external rectifier mount on the alternator. this will last longer. you do have the large capacitor at the amp input I believe .


May i remind you that the problem is the alt that failed IS (or was) bigger than the factory 78A. I just think its crazy how the 78A never failed because that thing was stressed out just running the stock accessories! (Especially at night with the lights and fan on high).. and now this brand new 95A kicks the bucket at 3 months old. I guess thats what you get for a non-GM product. The guy i got it from specializes in electrical equipment, i even told him i had a big sound system so i'm just surprised he gave me this "premium quality alternator" and not something better.

May i remind you that the problem is the alt that failed IS (or was) bigger than the factory 78A. I just think its crazy how the 78A never failed because that thing was stressed out just running the stock accessories! (Especially at night with the lights and fan on high).. and now this brand new 95A kicks the bucket at 3 months old. I guess thats what you get for a non-GM product. The guy i got it from specializes in electrical equipment, i even told him i had a big sound system so i'm just surprised he gave me this "premium quality alternator" and not something better.

think about these 2 alternators ? 78 , 95 not much difference.
also who determined what that amp capacity really is on the 95 amp ? under what conditions ?

you need a 140 amp minimum. you also must have the capacitors at the amp input to smooth out the surges.

another factor is heat load. this summer we had record heat .