What was found
COCKPIT TEMP UNCONTROLLABLE WITH LT PACK INSTBY. COCKPIT TEMP TOO HOT WITH LT PACK IN STBY NORMAL, TOO COLD WITH STBY COLD. TRIM AIR ON-OFF HAD NO EFFECT. REPLACED TEMP CONTROL VALVE LT PACK. TEMP VALVE ERRATIC ON EICAS. FOUND D2966 PIN 1 IS GROUNDED AND OPEN. REPLACED COMP SENSOR TS41 AND CK WIRING FROM SENSOR TO LT PACK CONTROLLER CHECKS OK . REPLACED PACK LOW LIMIT CONTROL VALVE IAW MM & SENSOR TS5133, ON LT PACK, NO HELP. ALSO TEMP CONTROL VALVE, NO HELP. REPLACED PACK OVHT SWITCH IAW MM, NO HELP. REPLACED STANDBY CONTROLLER, FAILED LAMP TEST. REPLACED STANDBY CONTROLLER AND OP CHECKED GOOD.