What was found
AIRCRAFT WAS GROUNDED. DURING CLIMB, THE CREW REPORTED THE AUTO PRESSURIZATION SYSTEM FAILED. NO EMERGENCY DECLARED. RETURNED TO DFW AND LANDED WITHOUT INCIDENT. PRESSURIZATION FLOW LIGHT ILLUMINATED AT FL 30000 WITH CRUISE POWER (300-400 FPM). GOOD PACKS, GOOD FLOW, REMAINING CONTROLLER WOULD NOT FULLY COMPLY UNTIL BELOW 12000 AIRCRAFT ALTITUDE, OUTFLOW VALVE FULLY CLOSED. REMOVED AND REPLACED LEFT AND RIGHT COOLING TURBINE ASSEMBLIES. OPERATIONAL CHECK GOOD. SEE ALSO AALA20170314007.