What was found
DURING CRUISE, UPPER CABIN AND ALL DECKS TEMPERATURE EXCEEDED 60 DEGREES C. RETURNED TO DEPARTURE. EMERGENCY NOT DECLARED. TROUBLESHOOTING FOUND A DEFECTIVE ZONE TEMPERATURE CONTROLLER. CONTROLLER WAS REMOVED AND REPLACED, OPERATIONAL SYSTEM CHECK SATISFACTORILY PERFORMED PER AMM 21-61-01 AND 21-61-00, AIRPLANE RETURNED TO SERVICE.