What was found
UNABLE TO CONTROL COCKPIT AND CABIN TEMPERATURE NORMALLY OR WHITHIN NORMAL LIMITS. ALSO REPORTED FWD CABIN TEMP UNCONTROLLABLE. IN AUTO, WITH SWITCH AT 12 O`CLOCK POSITION. FWD CAB TEMP AND SUPPLY FALL TO 0 DEG C. CONTROL CAB GOES HOT. WITH CONTROL CABIN FULL COLD, AND FWD CABIN FULL HOT, COCKPIT GETS WARM, FWD PAX CABIN ROW 1-8 ARE COLD. RT PACK TEMP = 0DEG C, LT PACK = 35DEG C, AFT CAB CONTROLLER SEEMS TO WORK. WITH TRIM AIR SWITCHED TO OFF, AFT CABIN WENT TO 0 DEG C, ALSO. ACFT GROUNDED. PERFORMED NR 2 ZTC BITE. FOUND FAULT FLT DECK ZONE TRIM VALVE. INSPECTED AND FOUND NR 2 ACAU FAULTY. REMOVED & REPLACED NR 2 ACAU 21-51-02. REF 21-62, TASK 834. PERFORMED ACAU OPS TEST IAW 21-51-02-710-802-002. SYS CKS NORMAL.