AC (?) noise

'02 Yukon Denali XL.
There is a noise that is coming from the AC compressor area of the motor, but don't know if its that, or another pulley. Best sound description I can compare it to is the typical ford whining steering punp, the whining increases with engine speed until it cuts out.

It doesn't always make the noise. I might hear it most times when accelerating or at idle for several days, then it will disappear, and won't hear it for several, then it comes back. The AC is blowing out cold air. The noise, at least at idle, starts when the AC compressor kicks on, and sometimes will stop once it shuts off, other times it keeps making the noise

Any ideas?

These AC compressors are known for slugging, as the compressor sits real low on the engine. My 2005 had similar noise, then started breaking the small AC belt about 3 times. See http://www.automotiveforums.com/vbulletin/showthread.php?t=1143054 , since I did this, haven't had noise or belt issue.

These AC compressors are known for slugging, as the compressor sits real low on the engine. My 2005 had similar noise, then started breaking the small AC belt about 3 times. See http://www.automotiveforums.com/vbulletin/showthread.php?t=1143054 , since I did this, haven't had noise or belt issue.

Thanks, I was afraid thats what it would be. Not going to be a cheap fix.