What was found
AIR-TURNBACK, AFTER T/O CABIN AUTO INOP MSG AND A/C WAS NOT PRESSURIZING WITH NR 1 SWITCHED TO AUTO CONT NR 2, NO CHANGE. MANUAL CONTROL OF OUTFLOW VALVE WORKED OK. RETURNED TO PHX. REMOVED AND REPLACED NR 1 AND NR 2 CABIN PRESS CONTROLLERS IAW 21-31-04 AND CABIN PRESS OUTFLOW ACTUATOR IAW 21-31-04. TT FOR CONTROLS 0081408 S/N 02400-0008957, S/N 07766. TT OUTFLOW ACT 0083127, S/N 04758. (M)