My compressor or clutch is chattering (best way to describe the noise). The AC blows ice cold. What kind of noise does a bad compressor make? What kind of noise does a bad clutch make? I really don't want to open up a perfectly charged AC system (change out compressor). I hear this "chatter" on many older vehicles, i guess to say it is the most common noise you hear that comes from the compressor area. FYI, I have a 98 Navigator w/ rear AC. Belt is in good shape, I topped off the AC (4oz freon) and no change in noise.