I own a 2003 Z71 Silverado ext. cab. When my a/c is on and ONLY when it's on I have a repetitive squeak that sounds like it's coming from just behind the dash just a little under the steering wheel, or in that general area. It's just squeak, squeak, squeak about every second. I can drown it out with just a little stereo volume, it's not loud, just annoying and the a/c works perfectly. Any suggestions?