What was found
(CAN) DURING CLIMB, A/C WOULD NOT PRESSURIZE. SUSPECTING AN OPEN DOOR OR POSSIBLE DAMAGE, ELECTED TO RETURN. IAW AMM MX PERSONNEL INSPECTED A/C AND FOUND NO DEFECTS WITH PRESSURE VESSEL AND ALL DOORS CLOSED TIGHT WITH NO DAMAGED SEALS. T/S OF PRESS SYS REVEALED OUTFLOW VALVES WERE WORKING CORRECTLY. SUSPECTING A FAULTY CONTROLLER, A/C RETURNED TO SERVICE USING MEL RELIEF FOR THE PRESS SYSTEM. THE NEXT DAY A/C RETURNED TO ITS PRIMARY MX BASE, FURTHER T/S REVEALED A SEIZED AUTOMATIC FLOW CONTROL VALVE LOCATED IN THE EE BAY WAS THE CAUSE. THE VALVE WAS REPLACED AND A/C PRESSURIZED CORRECTLY. TO FURTHER ENSURE THE DEFECT WAS CORRECTED, A TEST FLT WAS ISSUED. A/C PRESSURIZED AS REQUIRED DURING TEST FLT.