What was found
REPEAT GRIPE. TWO HOURS INTO FLIGHT THE FLIGHT DECK TEMP WAS UNCONTROLLABLE. NO EICAS OR LIGHTS. BITE PACK CONTROLLER AND ZONE CONTROLLER, NO FAULTS. INBD CREW COMMENT, STDBY OPS NORMAL. DEFER AUTO MODE FOR FURTHER T/S. PERFORMED BITE TEST PER M M 21-51-14. BITE SHOW "ALTITUDE SWITCH" AND" LOW LIMIT VLV" FAULT LIGHT ON. REPLACED ALTITUDE SWITCH, RETEST SHOW LOW LIMIT VLV. PART NST IN SEA 643-9025. PARTS: (563-3041) 625878-1 SWITCH. REPLACED LOW LIMIT VALVE PER AMM, CHECKS OK BUTTERFLY SHEARED ON SHAFT OF OLD VALVE. RPLC'D ZONE TEMPERATURE CONTROLLER (P/N S210T130-77 - SERIAL#104), RETURNED SYSTEM TO OPERATIONAL.