What was found
IN CRUISE FLIGHT FL250, SMOKE WAS NOTED IN THE CABIN AREA. THE PILOT DIVERTED FROM THE INTENDED ROUTE AND LANDED. ON EXAMINATION IT WAS DETERMINED THAT THE AUX CABIN HEATER WIRING FOR THE HEATING ELEMENT (INTERNAL TO THE UNIT) INSULATION WAS SMOKING. THE HEATER UNIT WAS R & R. THE ORIGINAL HEATER UNIT WAS RETURNED TO THE MFG FOR EVALUATION. THE AUX CABIN HEATER RELAY WAS REPLACED AS A PRECAUTION AND WAS ALSO RETURNED TO THE MFG FOR EVALUATION. A FUNCTIONAL TEST OF THE SYS WAS PERFORMED FOLLOWING REPLACEMENT OF HEATER AND RELAY. NO DISCREPANCIES NOTED.