As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW REPORTED THAT THE CABIN TEMPERATURE WOULD NOT GO BELOW 35 DEGREES CELSIUS AND RETURNED TO DCA. THE AIRCRAFT WAS FERRIED TO DAY WHERE MAINTENANCE INSPECTED AND REPLACED THE ENVIRONMENTAL CONTROL UNIT IN ACCORDANCE WITH DORNIER MAINTENANCE MANUAL 21-00-00. OPERATIONAL CHECKS WERE PERFORMED AND THE AIRCRAFT WAS RELEASED FOR SERVICE.