As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LGA - FLT 2323, ON CLIMB-OUT FROM LGA, THE AIRCRAFT WOULD NOT PRESSURIZE. FLIGHT RETURNED TO FIELD AT LGA AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE FOUND THE RIGHT PACK 35 DEGREES SHUTOFF VALVE HAD FAILED CLOSED. REMOVED AND REPLACED RIGHT PACK 35 DEGREE SHUTOFF VALVE AND TEMPERATURE CONTROL BOX. LEAK CHECK AND OPERATIONAL CHECK GOOD. (M)