What was found
AFTER ENGINE START AND PACKS WERE PLACED ON, "ZONE TEMP" LIGHT ILLUMINATED ON FORWARD CAB. BOTH MASTER CAUTION LIGHTS ILLUMINATED ALONG WITH AIR CONDITIONING LIGHT. LIGHTS WOULD NOT RESET WHEN MASTER CAUTION PRESSED. FWD CAB TEMP CONTROLLER KNOB HAD NO EFFECT ON TEMPERATURE GAUGE. GROUNDED - YES. P/Z TEMP CONTROL 2 SHOWS CABIN SENSOR ZONE FAULT. UNABLE TO RESET. REPLACED FWD CABIN ZONE TEMP SENSOR AND CHECK OK REF AMM 21-61-00. REPLACED NR 2 ACAU PRECAUTIONARY AND CHECK OK REF AMM 21-51-02. RAN BOTH PACKS, FWD ZONE TEMP CONTROL DOES NOT RESPOND. REMOVED AND REPLACED FWD TRIM ZONE VALVE REF AMM 21-61-21, CHECKS OK REF AMM 21-61-00-700-806-002 CABIN TEMP CONTROL OP TEST OK REF AMM 21-61-00-700-807-002.