What was found
L DUCT PRESSURE 15 AT IDLE R 30 PSI. OK IN CLIMB - CRUISE - DESCENT. REPLACED AIR SUPPLY CONTROL CARD M859, NO HELP. REPLACED HIGH PRESSURE CONTROLLER, NO HELP. UNABLE TO GET AIR PRESSURE OFF LEFT ENGINE. RAN TO 80 PERCENT N1 STILL NO AIR. PER TROUBLESHOOTING, L ENG HPC NEEDS TO BE REPLACED. REPLACED HIGH PRESSURE CONTROLLER, NO HELP. REPLACED NR 1 ENG PRV AND PRV CONTROLLER (P/N 2780539-107)-1721) & (P/N 792755-8) -82). RAN ENGINE BLEED OPERATES NORMALLY.