What was found
DIVERTED INTO EWRZONE TEMP DROPPED TO 38/49/26. TRIM AIR WAS MEL'D FL 370, NO A/ICE, TRIED AUTO, N, W ON PACK CONTROLLER. TEMP CONTINUED TO DROP IN ALL SETTINGS. LOST 30 DEGREES IN 50 MINS. ETURNED TRIM AIR PRESSURE REGUALTING VALVE TO NORMAL CONFIG. REMOVED AND REPLACED ZONE TEMP CONTROLLER AS PER MM 21-61-03-4 AND REMOVED AND REPLACED LT PACK TEMP CONTROL VALVE AS PER MM 21-51-12-4. BOTH VALVES LEAKED CHECKED GOOD, BOTH VALVES AND SYSTEM OPS CHECKED GOOD AS PER MM 21-61-00-5. CLEARS PIREP, OK FOR SERVICE.