Hello, new guy here.

I have a 1999 Silverado 2500 Extended Cab. When I turn the fan/air/heater **** on (on the dash), I instantly hear a noise under the hood. It's not a good noise like a motor running, but more of a whining noise. Any ideas?

Don't have much money, am unemployed, so am looking for a way to fix this. Not too mechanically inclined. By the way, no matter if I just have the fan on, the heater or the air, the noise is the same. When I turn the **** off, the noise goes away.

Please geel free to contact me directly (mgd@teleport.com).

I really appreciate hearing from you.

Greg

 

Two things come to mind.

First, a leak in the vacuum system or a crack in the heater control unit.

Second, either a fan touching a housing or a fan bearing out of round(fan may be getting ready to go?)

If you can reproduce this noise at idle, it shouldn't be too hard to track down and fix with the vehicle parked...

 

I'm thinking a\c compressor....if you have the mode set the defrost, or defrost\foot the a\c will automatically turn on to help defrost the windshield.
try unpluggng the a\c compressor to see if the noise goes away