As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKE OFF, THE CREW AND PILOT NOTICED AN INEXPLICABLE HEAT RADIATING THROUGH THE AIRCRAFT ACCOMPANIED BY A SMELL OF BURNING PLASTIC. HEATER, AIR CONDITIONER AND DEMISTER WERE IN THE OFF POSITION. WE WERE ONLY A FEW MILES AWAY FROM BASE AND RETURNED TO BASE WITHOUT ISSUE AND CONTACTED MAINTENANCE. UPON INSPECTION BY MAINTENANCE PROBLEM COULD NOT BE DUPLICATED, NO DISCREPANCIES WERE FOUND.