Howling Noise when air conditioner is on

I have taken my 2005 Chevy Colorado into 3 different dealerships (at least 10 times) for the past year (purchased it in Dec 2004), regarding a howling noise that occurs when the a/c is running. FINALLY, a month ago, the latest dealership said that a GM Bulletin was issued regarding this and that they could fix it. They diagnosed that the a/c cable had to be re-routed. It was in the shop for 3 days---I got it back and the noise was still there and WORSE! I contacted GM's hotline and advised them that I wanted to turn in my vehicle under the lemon law. A week later, the rep calls me to advise me that their "engineers" decided that this problem that so many of us are experiencing was "a general (common) noise" and they would not attempt to fix it anymore and that I could not turn my vehicle in under the lemon law! They refused to give me the name and number of the head of GM, but only gave me an address to GM in Detroit.

Anyone else getting this response? HELP??????

Can't help, but I have an S10 pickup with a similiar deal. I replaced everything in the AC system, and still have the howling noise at a certain rpm, just at about 60 mph where I drive mostly. Poor design is all I can come up with. Thinking about adding a muffler to the system. This is just a small tank that smooths out the compressor pulses. Might take your truck to a good AC shop, not a GM place, and see if one of the guys can solve the problem. Send the bill to GM.