something wrong with my alternator?

[gold84gmc]

after my old alternator crapped to bed, i got a used alternator(only because it was cheap) and it makes a "whining" noise and the pitch gets higher with the rpm's, when i drive down the highway at 55 thats all people can hear when i go by, is a whining...i already tested it and its charging how its supposed to, so is there bearings inside that might be bad?

[Layne]

The bearings could be a little dry. I'd shoot them with a little wd-40

[Irish_Alley]

it def sounds like bearings but if you do shoot with wd them its just prolonging the problem. also the wd will attract dust and dirt making the parts fail i would just go to the zone or something and buy a llt Warranty alt for 40-80 bucks

[gold84gmc]

also my belts squeel when the air is damp or if its raining, its not the alternator because it did it before i put that on, and it doesnt do it any other time, just when its raining or damp outside....theyre newer belts too

[Jim Rockford]

WD-40 isn't a lube and the bearings are sealed if its the newer style and if you tighten the belt too much  if its a v belt system, you will ruin the bearings .