What was found
CONT CAB ZONE TEMP LIGHT ILLUMINATED. GROUNDED - YES. REL PER MEL 21-21G. FLIGHT DECK PRI TEMP CONTROL INOP. INITIAL EVALUATION, CONT CAB ZONE TEMP LIGHT ON RECALL, RESET W/ MASTER CAUTION. PERFORMED PACK TEMP CONT BITE ON PZTC #1 & #2 IAW B737-900 FIM 21-62 TASK 801. ZONE TRIM VALVE LIGHT COMES ON. RE-RAN BITE PROCEDURE AND FAULT CLEARED. OPERATED BOTH PACKS INDEPENDENTLY, AND THEN TOGETHER, 5-10 MINS EACH. FAULT DID NOT COME BACK. RE-RAN BITE, CHECKS GOOD. THIS MTX ACTION CLEARS MEL 21-21G.