What was found
AIR CONDITIONING DUCT PRESSURE SPLIT GREATER THAN 20 PSI. CLIMB LEFT DUCT WAS 15 RIGHT DUCT WAS 45, CRUISE LEFT DUCT WAS 21 RIGHT DUCT WAS 45 . PRESSURIZATION WAS NORMAL . GROUNDED - YES. PERFORMED DUCT PRESSURE LOW ENGINE BLEED SOURCE B737-900 FIM TASK 36-10 TASK 804. FOUND PRSOV VALVE FAULTY. R/R PRSOV REF B737-900 AMM 36-11-04-400-801. PERFORMED ENGINE BLEED AIR CROSSOVER OPS TEST PER AMM 36-11-00-710-80. DUCT SPLIT STILL EXITS. CHANGED BLEED AIR REGULATOR PER AMM 36-11-03, NO HELP. R/R BLEED AIR THERMOSTAT REF AMM 36-11-05 NO HELP. DURING TROUBLE SHOOTING FOUND BLEED AIR FLEX LINE FROM THERMOSTAT SENSOR LEAKING, REPLACED FLEX AS REQUIRED, PERFORMED BLEED AIR CROSSOVER OPERATIONAL TEST REF AMM 36-11-00-710-801 SYSTEM OPS CHECKED NORMAL.