As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT RETURNED OF FLIGHT AS A CONSEQUENCE OF PRESSURIZATION FAILS. CAPTAIN REPORTED THAT LEFT AIR CONDITIONING PACKAGE WAS INOPERATIVE AND RIGHT AIR CONDITIONING PACKAGE WITH A FEW FLOW. AIRCRAFT WAS SENT TO THE HANGAR. DURING OVERNIGHT SERVICE BOTH PACKAGES WERE CHECKED BY LEAKS IAW MM 36-00-00 AND A LEAK WAS DETECTED IN GROUND PNEUMATIC VALVE. GROUND PNEUMATIC VALVE WAS REPLACED IAW MM 21-32-00, TEST CORRECT.