As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SJU FLT 1078 EN ROUTE SJU TO PHL. DURING CLIMB, WITH LEFT PACK ON MEL, THE RIGHT PACK DUCT PRESSURE WAS 10 PSI. ALMOST NO AIRFLOW, HAD TO SELECT L BLEED TO SUPPLY AIR TO THE RIGHT PACK. THE CREW DECLARED AN EMERGENCY AND RETURNED TO FIELD SJU. THE FLIGHT LANDED WITHOUT FURTHER INCIDENT. THE AIRCRAFT WAS MAINTENANCE FERRIED TO PHL. MAINTENANCE REPLACED THE RIGHT ENGINE PRESSURE REGULATING AND SHUT-OFF VALVE.