1996 Honda Accord clunking sound when fans come on

Today I had my a/c compressor, expansion valve, receiver/dryer and new 0 rings replaced in 1996 honda accord EX 2.2L 4cylinder. After driving it for a few minutes I began hearing a clunking noise every couple of minutes or so. When getting it home, I popped the hood and noticed that the clunking noise was coming on when the two fans cut on and seemed to be coming from somewhere near the new receiver/dryer. The air in the car was not normally as cool as it used to be. What is the problem. Its hard to believe that the mechanic wouldnt notice this before giving it back to me.