I have looked through the threads and haven't been able to clearly find an answer to my problem so I'm going to post it. Forgive me if its already been addressed.

My A/C compressor on my 1999 f-150 is making a hollow grinding type noise is the best way I can describe it. There is an accumulation of black dust around the backside of the pulley. It does it mainly on a cold start (but not every time) then quiets down to a squeak when the A/C is on. The other day the A/C stopped working completely, then after I turned the truck off it started working again. What are your opinions on what this is and what should I do to fix it. The clutch is working fine so it seems. It engages and disengages when its supposed to. Is it my compressor going bad or my clutch bearing? Any help would be appreciated.