I got an 83 z28 Crossfire inj 5.0L, and when i got the car a year ago the alternator was fine, but since 3 months ago it would sometimes squeal when i put the air on, and has just gotten worse, well the alternator seems fine, when the car starts when the engine is cold the gauge reads probably 18v. im sure it reads normal, its above the halfway mark i forget what volts it says half way, but it would be fine untill i turn the lights on then the gauge would drop a little then the high beams would make it drop a little, the if i just put the air on with the fan low it would go to the middle of the gauge then if i put the fan on high the gauge goes low and the belt squeals, well eventually it would squeal after the car is warmed up, so i replaced the belt and made it pretty tight and after a while it squealed again, but even with the new belt on the gauge would drop more and more with the accesories i put on like the lights air, not so much when i put the heat on, but putting the windows down and having the wipers on, and thats just idling, then if i have the lights on and put the car in drive the gauge goes down alot more, not quite in the red but the car just barely stays running. so what could the problem be?? the squealing is very annoying and embarassing, but i know its not normal for the volts to drop when an accesory is on, thanks for the help!



ALSO I LISTENED TO THE ALTERNATOR WITH A SCREWDRIVER UP TO MY EAR WITH THE CAR IDLING AND IT WASN'T SQUEALING OR ANYTHING AND THE VOLTS WERE GOOD, I DID HEAR A LITTLE GRINING NOISE, I'M GUESSING THATS BAD? AGAIN THANKS FOR THE HELP!

 

It probably needs replaced. Take it to Autozone and have them test it for free.