As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE AIRCRAFT WAS GROUNDED. CABIN WOULD NOT COOL BELOW 75 DEGREE WITH BOTH ZONE TEMP VALVES FULL COLD. BOTH DUCTS PRESSURE READ BETWEEN 20-25 PSI. BOTH DUCT TEMPS INDICATED APPROX 75 DEGREE. THE FLIGHT DECLARED AN EMERGENCY AND RETURNED TO PHX WITHOUT FURTHER INCIDENT. REMOVED AND REPLACED THE LEFT HAND ENGINE PRE-COOLER VALVE, OPS AND LEAK CHECKS GOOD IAW MM 36-12-02. (SEE ALSO SDR AALA201706209019)