Haas Alarm: 644 (M) APC-LOW AIR PRESSURE – A low air pressure condition was detected during pallet changer operation. Check that the air supply is 100 psi, minimum. Check that the air supply line is the correct diameter. Check that the mill pressure regulator is set to 85 psi. If this alarm continues to occur, check the entire pressurized air system for any abnormal air leakage.