Expert: Skip Bollinger - 7/6/2007

Question
Whenever I am accelerating or maintaining higher speeds (40-50 mph), my compressor "chirps" when it engages. I've had the idle pulley and serpentine belt replaced, but the noise continues. My mechanic says I need a new compressor. What are your thoughts?

Answer
Heather,
  I am a Parts Professional, NOT a tech but will offer my thoughts...
  I have NEVER seen a compressor chirp. The noise has always been from the belt OR debris built up on the pulley. You didn't tell me what year your GMC is. What I would do is 2 fold,
1.  I would start the vehicle and have someone give it gas to see if it will chirp in the driveway. If it will, take a plant mister with water in it and spray the belt (carefully on the pulley side) to see if the noise goes away. If it doesn't,
2.   I'd spray carburetor cleaner on the belt and take it out and drive it immediately. If that helps, I'd remove the belt and clean ALL the pulleys it goes around.
  Chirping is NORMALLY a belt problem. It could be a problem with debris on the pulleys. ANY rotating device such as an A/C compressor, Alternator, Smog Pump, Idler Pulley or Power Steering have bearings which will "growl", not chirp.
  Heather, I hope this helps. Like my Profile says, I'm a Parts Professional, NOT a tech. I know, in this occupation, not too many people will agree. I'm giving you my best guess. Thank you for your question..
Skip