What was found
PRIOR TO TAXI, AFT CABIN ZONE TEMP AND AIR COND LIGHTS ILLUMINATED ON MASTER CAUTION RECAL AND RESET CLEARED IT. UNABLE TO CONTROL TEMP IN AFT CABIN. AIR SUPPLY DUCT TEMP STABILIZED AT 46 DEGREES C AND COULD NOT BE CONTROLLED. PASS CABIN TEMP STABILIZED AT 39 DEGREES C. ACFT GROUNDED. PERFORMED PACK/ZONE TEMP CONTROLLER BITE PROCEDURE, REF 21-62, TASK 801 FIM, TRIM VALVE ZONE LIGHT ON AND CLEARED WITH VERIFICATION. PERFORMED AFT CABIN TRIM AIR VALVE-FAULT ISOLATION IAW FIM 21-62, TASK 835. NO CURRENT FAULTS, INTERMITTENT FAULT, NO HISTORY PAST 30 DAYS.