air condition problem
 

I have a 2001 Honda Civic LX. Last night I noticed a knocking in my
motor area. It's not steady like a rod knocking but more of an off
rhythm knocking. It does not always knock either. When it is knocking I
can get it to stop instantly by turning off the A/C. What is causing
this knock? I'm sure it needs repair but I need to know what to talk
about with a repairman, and generally what to expect in cost. I would
also like to know if this is something that has to be fixed immediately
or can I still use my A/C for awhile without doing more damage resulting
in much more expenses? Thank You -William (from Carolina Beach NC)