DRIVING 25 MPH AND TURNED KNOB TO PUT ON HEAT AND THICK, BROWN SMOKE COMING OUT OF VENTS IMMEDIATELY FILLED CAR. I STOPPED AND LOOKED UNDER HOOD. I COULD SEE A PIPE WHERE SMOKE SEEMED TO BE ORIGINATING BUT DON'T KNOW WHAT IT IS CALLED. WHEN SMOKE CLEARED AND I DIDN'T SEE ANYTHING LEAKING UNDER THE CAR, I STARTED TO DRIVE AS CALLED SERVICE STATION A FEW BLOCKS AWAY. THEY SAID TO BRING IT OVER BUT UPON DRIVING ABOUT 50 MORE FEET SMOKE GOT WORSE; BECAME THICKER AND BLACK. I STOPPED AND TURNED ENGINE OFF AND GOT OUT OF THE CAR AND WHEN I TURNED TO LOOK AT THE CAR, IT WAS ALREADY UP IN FLAMES COMING FROM UNDER THE HOOD. IT TOOK ONLY A COUPLE OF MINUTES AND THE ENTIRE CAR WAS ABLAZE. *TR