What was found
CREW TOOK OFF ON A MISSION & SMELLED A BURNING ODOR. IMMEDIATELY TURNED OFF AIR CONDITIONING & RETURNED TO BASE. PILOT FOLLOWED ODOR TO LT TRANSMISSION AREA & NOTICED AIR CONDITIONING BELT HAD FAILED. TRIED TO TURN THE AIR CONDITIONING COMPRESSOR & FOUND IT DIFFICULT TO TURN. INSPECTED ACFT & AIR CONDITIONING SYS AS REQUIRED & DEFERRED AIR CONDITIONER. REMOVED BELT & PLACED ITEM ON MEL. AIR CONDITIONING COMPRESSOR FAILED & TOO MUCH LOAD FOR BELT TO SUPPORT. BURNING ODOR CAUSED BY THE BELT SLIPPING ON COMPRESSOR PULLEY. AIR CONDITIONING COMPRESSOR HAS BEEN REPLACED & HAS BEEN RETURNED TO SERVICE.