What was found
AMBER CABIN ALTITUDE CAS MESSAGE ILLUMINATED AT APPROX 36,000 FT, FOLLOWED SHORTLY AFTER BY THE RED CABIN ALTITUDE CAS MESSAGE. PERFORMED PRESSURIZATION CONTROLLER BUILT-IN-TEST. NO DEFECTS NOTED. PERFORMED MANUAL PRESSURIZATION OF ACFT WITH APU. NO EXTERNAL LEAKS ON ACFT NOTED. PERFORMED VISUAL INSPECTION OF CABIN OVERFLOW VALVES, PLUMBING AND CONTROLS. NO DEFECTS NOTED. RAN ENGINES AND FOUND LT ENGINE UNABLE TO PRESSURIZE ACFT. RT ENGINE PRESSURIZED ACFT NORMALLY. REMOVED AND REPOSITIONED ENGINE FLOW CONTROL VALVES. RT ENGINE WAS THEN UNABLE TO PRESSURIZE THE ACFT. REMOVED FAULTY FLOW CONTROL VALVE AND REPLACED WITH EXCHANGE UNIT. LEAK AND OPS CHECKS NORMAL, CLOSED ACCESS PANELS. SERVICEABLE FLOW CONTROL VALVE PLACED IN ORIGINAL POSITION. WORK COMPLETED IAW MM CHAPTER 21-30-00, AND 21-10-00.