I have a c230 2002 coupe and i`ve been having problems with tha ac sometimes it works and some times it shuts of is there a special sensor I should look up

 

If you mean (sometimes it works and sometimes it shuts off) that the blower stops and starts erratically, it could be the blower motor relay, which was defective in my C230 as well.
On my '05, it's a small rectangular black box located on the outside of the blower itself.

 

no is not the blower that shuts off the thing is that cold air stop from coming out