What was found
TWO AIR CONDITIONING SHUTOFF VALVES ARE INSTALLED. DURING CLIMBOUT, THE AIRCRAFT WAS PRESSURIZING BUT NOT AT A RATE SUFFICIENT TO ACHIEVE CRUISING ALTITUDE. THE FLIGHT RETURNED TO BASE AND TROUBLESHOOTING REVEALED THE RIGHT AIR CONDITIONING SHUTOFF VALVE HAD FAILED CLOSED. REPLACING THE VALVE RETURNED PRESSURIZATION SYSTEM OPERATION TO NORMAL. AFTER RESEARCHING FLEET DATA WITH THE A/C MFG, IT TURNS OUT THIS VALVE IS NOT A HIGH FAILURE ITEM. ALSO, THE CREW HAS PROCEDURES IN PLACE TO OPERATE THE AIRCRAFT WITH ONE VALVE NOT FUNCTIONING.