What was found
AIRCRAFT RETURNED DUE TO AIR CONDITIONING SYSTEMS FAILED, RT SYSTEM WAS SHUTDOWN, LT SYSTEM DID NOT OPERATE AND SMOKE ODOR WAS DETECTED. DURING MAINTENANCE CHECK, THE CHIP DETECTORS WERE CHECKED, WATER SEPARATORS WERE REPLACED IAW MM 21-20-2, BITE TO BOTH CONTROLLERS WAS PERFORMED IAW MM 21-32-00 AND SMOKE ODOR CHECK WAS PERFORMED IAW MM 21-30-00, ALL CORRECT. ADDITIONALLY, THE LT FAN WAS REPLACED IAW MM 21-20-06, TESTED CORRECT. NO OVERWEIGHT INSPECTION WAS NOT REQUIRED DUE TO AIRCRAFT LANDED WITH 118,478 POUNDS AND MAXIMUM LANDING WEIGHT IS 128,000 POUNDS. DURING TRANSIT CHECK, THE RT AIR CONDITIONING SYSTEM FAILED AGAIN, SO PRESSURE REGULATOR VALVE WAS REPLACED IAW MM 21-31-1, TESTED CORRECT.