WHILE DRIVING THE VEHICLE AT NORMAL SPEEDS & OPERATING THE AIR CONDITIONER BLOWER MOTOR ON LOW SPEED, THE DRIVER OF THE VEHICLE NOTICED SMOKE COMING FROM THE BELOW THE DASH BOARD ON THE PASSENGER SIDE OF THE VEHICLE. AS THE SMOKE PROGRESSED, THE DRIVER SOON OBSERVED FLAMES AND MELTING PLASTIC DRIPPING OFF OF THE HVAC BOX. THE DRIVER IMMEDIATELY PULLED OVER, OPENED THE [PASSENGER DOOR AND EXTINGUISHED THE FLAMES WITH A 10 BAC FIRE EXTINGUISHER. WHEN THE VEHICLE WAS BROUGHT INTO THE MESA COUNTY FLEET REPAIR FACILITY, WE NOTICED THE HEAT SOURCE ORIGINATED FROM THE BLOWER MOTOR AND RESISTOR AREA OF THE HVAC BOX. THE ELECTRICAL WIRING HAS MELTED INSULATION AND NO FUSES APPEAR TO HAVE BURNED.