As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 837 JFK-STI, AIR RETURN DUE TO - IN HIGH FLOW NR 1 PACK OFF AS PER MEL AND HOT AIR VALVE CLOSED COCKPIT AND CABIN TEMP CONTINUED TO RISE TO 80 ON COCKPIT 78 IN CABIN AND WOULD NOT COOL. REMOVED AND REPLACED NR 1 PACK FLOW REGULATING CONTROL VALVE IAW AMM 21-51-51, OPS AND LEAK CHECK GOOD.