What was found
COMBUSTION HEATER SWITCH TRIPPED WHEN PILOT ATTEMPTED TO TURN ON AIRCRAFT HEATER. PILOT RESET SWITCH AND HEATER OPERATED. PILOT NOTICED VOLTAGE METER PEGGED AND A HIGH RATE OF DISCHARGE FROM BATTERY. PILOT SMELLED ELECTRICAL BURNING SMELL AND TURNED OFF AIRCRAFT'S ELECTRICAL SYSTEM. INSPECTION REVEALED THE JANITROL HEATER COMBUSTION AIR BLOWER MOTOR HAD SHORTED TO GROUND INTERNALLY, AND CAUSED EXCESSIVE OVERHEATING AND FAILURE OF MOTOR.