Hello, My name is Steve and im going crazy! I have a 1999 chevy blazer and it is making a whining-whirly noise that I can not pinpoint. I was told that it was the belt tensioner pulley so I replaced it and still have the same problem. Now Im told its the bearings in the alternator but I replaced that 6 months ago! the ac does not work which I have had recharged in past and then it works fine. Recently the heater has quit blowing warm air so its down. The fuel guage doesnt work...I have seen post here so figured that out. My main concern is the noise ...it is loud!! Any ideas??

 

Remove the belt and check all pulleys for up/down play. Certain accessories have an acceptable amount of in/out play.

 

I had a similiar sound awhile back in the winter I noticed it 1st. It was the A/C Clutch, was noisy as all hell when it was cold then quietened down when it warmed up. To see if it is that pull the A/C plug/molex out of the A/C unit so it doesn't engage the clutch & start the truck. If that freakishly loud noise is gone... voila!