What was found
EN ROUTE FROM AVP TO MDT HAD SMOKE IN COCKPIT AFTER TURNING ON PROP HEAT SWITCH, THEN TURNED ON ALL ELECTRICAL POWER. AFTER A FEW MINUTES, TURNED POWER BACK ON, ALL WAS GOOD WITH PROP HEAT SWITCH LEFT OFF. AFTER LANDING IN MDT MAINTENANCE FOUND A BURNT SWITCH, MEL'D PROP. DE-ICE SYSTEM AND FLEW BACK TO AVP, INSTALLED A NEW SWITCH, OPS CHECKS GOOD.