What was found
ABQ - FLT 864 - ABQ-PHX - AIR TURN BACK, CREW UNABLE TO PRESSURIZE AIRCRAFT IN AUTO, STANDBY OR MANUAL MODES. AIRCRAFT RETURNED TO ABQ AND LANDED WITHOUT FURTHER PROBLEMS. MAINTENANCE GROUND PRESSURIZED AIRCRAFT, CHECKED OUTFLOW VALVES, DOOR SEALS AND BY-PASS VALVE. ALL OPS CHECK NORMAL. AIRCRAFT RETURNED TO SERVICE. (Z)