What was found
HOLDING NR 1, SUDDENLY GOT WARM IN COCKPIT. WINDOWS FOGGED, THEN EICAS COMPACTED. BOTH PILOT EADI/EHSI WENT FULL BRIGHT. THEN F/O'S EADI BLANKED. AIRCRAFT BACK TO BLOCK AND GROUNDED. CONDUCTED EQUIPMENT COOLING SYSTEM BIT, IAW B767 FIM 21-58 FT 873, NO FAULTS FOUND. CONDUCTED ZONE TEMP CONTROLLER BIT, IAW FIM 21-61 FT 872, NO FAULTS FOUND. REPLACED MANIFOLD INTERCONNECT VALVE, IAW AMM 21-58-01, OPERATIONS CHECK OK. CONDUCTED ENGINE RUN, IAW ABX ERU AND TAXI CHECKLIST, CPT AND F/O EADI AND HSI BLANKED, EICAS BLANKED. CONDUCTED PACK TEMP CONTROLLER BIT, IAW FIM 21-51 FT 803, NO FAULTS FOUND. INSPECTED RIGHT AND LEFT PACKS, FOUND TRIM AIR SHUT-OFF VALVE IN CLOSED POSITION AT ALL TIMES. REPLACED TRIM AIR SHUTOFF VALVE, IAW AMM 21-61-06, OPERATIONS CHECK OK. SEE LP 38047-11/3 FOR ENGINE RUN. UPON REPLACEMENT OF TRIM AIR SHUTOFF VALVE, REF L/P 35047-11/1. CONDUCTED ENGINE IDLE RUN W/PACKS FOR T/S, IAW ABX ERU AND TAXI CHECKLIST. CONDITIONS IN DISCREPANCY DID NOT RE-OCCUR AFTER 25 MINUTE ILDE RUN, COOLING SYSTEM OK.