What was found
THE FLIGHT CREW REPORTED THAT THEY WERE RECEIVING LESS THAN 5% OF AIRFLOW INTO THE CABIN FROM THE RT ENGINE PRESSURE SOURCE IN CRUISE FLIGHT. RT ITT IS 30 DEGREES COOLER THAN THE LT ENGINE ITT. BELOW 25000 FT RT ENGINE PRESSURE UNABLE TO PRESSURIZE CABIN ALONE. THE MAINTENANCE VENDOR TROUBLESHOT SYSTEM AND DETERMINED THE RT PRSOV DEFECTIVE. AN OVERHAULED PRSOV WAS INSTALLED. OPERATIONS CHECKS WERE SATISFACTORY AND THE AIRCRAFT WAS RETURNED TO SERVICE.