What was found
ON DEPARTURE AIRFLOW FROM PACKS WAS SO LOUD COMM WAS DIFFICULT TO IMPOSSIBLE. BOTH PACK CONTROLLERS UNRESPONSIVE. ALL WE COULD GET WAS VERY COLD AIR. CONT CAB @ 4C, FWD CABIN 12C, AFT CABIN 17 C. ALL STUCK/UNCONTROLLABLE. GROUNDED - YES. DIVERSION TIME 29 MINUTES - SUSPECT LEFT PACK FLOW CONTROL VALVE REMAINS IN APU HI-FLOW MODE. CHECKED WIRING FOR SHORT TO GROUND REF W/D 21-51-11-6, COULD NOT CONFIRM BAD WIRING. REPLACED L/H STANDBY TEMP CONT VALVE REF B737-800 MM 21-51-11-400-80, PACK ZONE TEMP CONT BITE TEST OPS NORMAL. BOTH PACK GREEN. REF AMM 21-61-00-200-806-002. NO LEAKS. REPLACED P5-10 PANEL OPS NORMAL REF AMM 21-51-65-400-801. RAN BOTH ENG.AT HIGH POWER WITH BOTH PACKS IN AUTO, TRIM AIR ON, TEMP CONTROL IN AUTO POSITION WOULD HEAT AND COOL A/C, OPS CK GOOD.