What was found
AIR CONDITIONING PANEL, ISOLATION VALVE APPEARS INOPERATIVE. ACFT GROUNDED. ON ARRIVAL, PACKS INOPERATION, ISOLATION VALVE INOPERATIVE. WOULD NOT CLOSE. NORMAL OPS WITH SWITCH. FORCEFULLY JIGGLED SWITCH TO OFF POSITION, THE ISOLATION VALVE OPS NORMAL OPENED AND CLOSED. VERIFIED SWITCH INTERMITTENT. REPLACED AIR CONDITIONING MODULE, INCLUDING THE SWITCH IAW MM 21-51-65. OPS NORMAL, GROUND VERIFICATION ACCOMPLISHED.