What was found
DISCREPANCY: LEFT DUCT PRESSURE FLUCTUATES MORE THAN 20 PSI, NORMAL TO LOW RANGE AT TAKEOFF THRUST. STABLE AT CLIMB THRUST, FRM 36-10-01-01. CORRECTIVE ACTION: PERFORMED AIR SUPPLY BITE TEST PER AMM 36-23-00, FOUND L PRC WIRE FAULTS, REMOVED AND REPLACED LEFT ENGINE BLEED AIR CARD PER AMM 36-11-12, BITE CHECK OK. AC REMAINS ETOPS 180