As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED SMOKE IN THE COCKPIT UNKNOWN LOCATION. UPON INVESTIGATION BY OUR LEAD MECHANIC WE FOUND THE HEATER FLAMED OUT. OPS CHECKED GOOD NO DEFECTS WERE FOUND. AND AIRCRAFT RETURNED TO SERVICE. THE JANITROL HEATER WAS CLOSE TO TBO. AND WAS REPLACED WITH A OVER HAULED HEATER. THE FOLLOWING MONTH.