As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAKEOFF THE BLEED AIR HEAT CAME ON WITHOUT PILOT INPUT. PILOT ATTEMPTED TO TURN HEAT OFF WITH SYS SWITCH AND TEMP. CONTROL KNOB. NEITHER ACTION WORKED. COCKPIT WAS GETTING EXCESSIVELY HOT SO PILOT OPENED UP ALL AIR VENTS AND PULLED FIREWALL SHUTOFF VALVE FOR BLEED AIR HEAT. AFTER ACTUATING SHUTOFF VALVE POSSIBLE LIGHT SMOKE AND ODOR FROM A EXCESSIVELY WARM SYS WAS NOTED IN COCKPIT. PILOT DECLARED AN EMERGENCY AND RETURNED TO AIRPORT AND LANDED WITHOUT INCIDENT.