What was found
WHILE ACCOMPLISHING T.C. #NG-21EA-23228-1, #!1 PZTC HAS "THIS PACK - TCV" FAULT LOGGED. GROUNDED - YES. DUE TO HISTORY, REMOVED AND REPLACED LH PACK TEMP CONT VALVE V141, IAW B737-900 AMM 21-51-10-000/400-801, LEAK CHECKS GOOD. PERFORMED PZTC BITE IAW FIM 21-62 TASK 801, PASSES BITE, NO FAULTS. RAN BOTH PACKS 15-20MINS, NO LIGHTS ON RECALL. A/C OK FOR SERVICE. SYSTEM GROUND VERIFICATION SUCCESSFUL.