vegeta

So, I was driving home today and I heard a loud scratching/grinding noise. At first, I thought the COMAND was eating the CD....it almost sounded like a record scratching. After removing the CD, i noticed that the A/C is not working. After I got home, I tried turning it off and turning it back on and the grinding noise is there still there. Any idea what this could be? It is relatively loud too and the sound seems to be coming from the passenger side. I posted this on the SLK55 forum but thought I would post here also. Any help would be appreciated. Thanks!