AFTER I STARTED MY VEHICLE INSIDE MY GARAGE I TURNED THE HEAT ON. THE TRUCK WAS STILL IN PARK. AFTER I TURNED ON THE HEAT I WENT INTO THE HOUSE TO GET MY COAT. WHEN I CAME BACK OUT TO THE TRUCK TO PREPARE TO LEAVE I NOTICED SMOKE INSIDE THE VEHICLE. I IMMEDIATELY TURNED THE VEHICLE OFF AND REMOVED THE KEYS. I OPENED ALL FOUR DOORS TO LET THE SMOKE OUT, THE GARAGE DOOR WAS ALREADY OPEN. THE TIME FROM WHEN I STARTED MY TRUCK TO WHEN I SAW THE SMOKE WAS ABOUT 15 SECONDS. I LET THE TRUCK SIT FOR ABOUT AN HOUR BEFORE I STARTED LOOKING FOR WHAT COULD HAVE CAUSED THE SMOKE. I REMEMBERED THAT THE SMOKE DIDN'T START UNTIL AFTER I TURNED ON THE HEATER SO I IMMEDIATELY CHECKED ALL RELEVANT FUSES AND RELAYS WHICH WERE GOOD...NONE WERE BLOWN. I THEN SET ABOUT CHECKING THE FAN, AND AS I REMOVED THE RESISTOR FROM THE FAN HOUSING UNDER THE DASH AND UNPLUGGED IT I SAW THAT IT (THE RESISTOR) WAS BURNED AT ONE OF THE BLADES.WITH SOME PLASTIC AROUND IT AND SCORCH MARKS AT ANOTHER BLADE. THIS PROMPTED ME TO INSPECT THE RESISTOR FEMALE RECEPTACLE ON THE WIRING HARNESS. I BEGAN INSPECTING THE RECEPTACLE. I FOUND A BURNED UP FEMALE BLADE RECEPTACLE. I DON'T KNOW IF THE RESISTOR SHORTED OUT OR THE WIRING HARNESS SHORTED OUT. I WENT TO THE AUTO PARTS STORE AND BOUGHT ANOTHER RESISTOR BECAUSE I NEEDED HEAT IN MY VEHICLE SO I PLUGGED IN AND REINSTALLED THE NEW RESISTOR AND STARTED UP THE TRUCK AND OBSERVED THE RESISTOR. NO SMOKE. I THEN TURNED ON THE HEAT (FAN) AND IT WOULDN'T CO