As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BETWEEN 16,000 AND 24,000 FEET, HAD A HARD TIME REGULATING CABIN TEMPERATURE. ONE PACK HAD ALREADY BEEN PUT ON MEL, EMERGENCY WAS DELCARED AND AIRCRAFT RETURNED TO DEPARTURE. AIRCRAFT LANDED WITHOUT INCIDENT. THE AIRCRAFT WAS GROUNDED. REPLACED COMPRESSOR DISCHARGE OVERHEAT SWITCH IAW 21-51-19-01.