HEATER SHORTED OUT CAUSING AN ELECTRICAL FIRE. FIRE ENGULFED THE WHOLE FRONT OF THE CAR INTO THE FRONT SEAT. THE VEHICLE WAS MOVING DOWN THE INTERSTATE. WE HAD THE HEAT ON SETTING 4. SMELLED LIKE SOMETHING WAS BURNING. TURNED OFF THE HEATER. WHITE SMOKE STARTED COMING OUT OF VENTS. DECIDED TO GET OFF AT NEXT EXIT AND GET IT LOOKED AT. PULLED INTO PARKING LOT, BLACK SMOKE STARTED POURING OUT OF THE VENTS. WITHIN A MIN. OR TWO THE FRONT OF THE CAR WAS ENGULFED IN FLAMES.