What seemed to me and sounded like the a/c compressor was seizing up in my 2000 GT turned out to be a frozen belt tensioner. It growled real bad with the a/c on which made me believe it was the a/c compressor. The dealer said its a common problem with 3800 Series II engines. However, they cracked the rear valve cover changing the tensioner. That tied up the car for 2 more days until a new one could be located. Has anyone else out there had a similar problem? If not, how about a rattling noise in the sunroof in the closed position?