Dusty alternator?

[biorob]

The alternator in my 08 yukon is screeching when I accelerate. I removed the serpentine belt and can hear the same sound when I manually spin the alternator pulley. The voltmeter occasionally drops from 14 to about 12 volts, but I'm not getting any instrument panel warnings. The GM service dept. claims that the noise is attributed to dusty conditions in the area. He recommended compressed air to blow out the excess dust. I used compressed air but the noise is still there. Any suggestions?

 

[07whitetahoe]

Dried bearings probably. Might be time to replace if you cannot stand the noise.

 

[taylorjm]

lol, I'm sorry, maybe it is due to dusty conditions, but it sounds like a load of BS to me. I mean, sure, I guess if it's extra dusty it can work it's way into the bearings quicker, but the compressed air isn't going to fix a bearing squeak. Maybe there's something else in there that can squeak that I don't know about, but that sounds like an answer you get from tech support.."ahh yes, go blow your alternator and if that doesn't work, call us back"

 

[biorob]

I could still hear the noise when I spun the pulley by hand but I replaced the belts (ahead of schedule) and the noise subsided. I replaced them with "gates" and noticed a pretty big difference in ply/thickness.

 

[stevek]

The voltmeter occasionally drops from 14 to about 12 volts, but I'm not getting any instrument panel warnings

FYI it drops from 14 --> 12 when the alternator doesn't need to produce electricity and it's running off the battery, if I remember correctly