As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HEATER SHOWED SIGNS OF ABNORMAL COMBUSTION IE. SOOT TRAIL FROM FUEL DRAIN VENT. UPON INVESTIGATION, FOUND COMBUSTION AIR BLOWER FAN WHEEL ASSY HAD COME APART AND FOD`D HEATER. FAN MOTOR WOULD STILL RUN AIR PRESSURE SWITCH HAD FAILED IN CLOSED POSITION. IAW AD AIR PRESSURE SWITCH DOESN`T NEED OPS TESTING. RECOMMEND THAT ALL COMBUSTION AIR PRESSURE SWITCHES BE TESTED AND THAT THE COMBUSTION AIR FAN WHEEL ASSY BE INSPECTED AT SAME INTERVALS AS CALLED FOR BY AD. (K)