WHILE PASSENGER SIDE VISOR IS DOWN SMOKE STARTS POURING OUT FROM UNDER THE HEAD LINER. WHEN THE VISOR IS PLACED BACK IN THE CLOSED POSITION SMOKE CLEARS OUT AND STOPS. PER THE MECHANIC, A SHORT IN THE ELECTRICAL SYSTEM HAS RESULTED IN A MELTED ELECTRICAL BOARD AND THE ENTIRE HEAD LINER AND ELECTRICAL BOARD NEEDS TO BE REPLACED. THE VISOR CAN NOT BE USED OR THE SHORT MAY START A FIRE INSIDE THE VEHICLE. THE VEHICLE WAS IN MOTION WHEN THIS OCCURRED. VAN FILLED WITH SMOKE QUICKLY. HAD TO PULL OVER AND OPEN DOORS TO CLEAR THE SMOKE.