A/C compressor trouble.

My A/C works fine blows cold air but it makes the most horrible hissing sounds (3 years now) Ive posted in here several times about it before but nothing has worked yet. What can I do to make it quieter? If the ac is working it is a lil bit quieter but when it disengages it makes the horrible noise. 2000 grand am se 3.4 v6 automatic. Could this be dirt in the compressor clutch bearings? Can I take it apart and fix it or is this one non servicable? The dealer says since it blows cold air its ok. The best way I can describe the sound when it is disengaged , sounds like a supercharger crappin out.