LED fog light bulbs
Fog lights shine low over the road surface and wide to the sides, so in fog, heavy rain or snow they light up the verge and the area immediately around the car. Replacing halogen bulbs with LED versions gives whiter or yellow light, lower power consumption and a longer service life. LED fog light bulbs are made with bases such as H11, H8, H16 or H3, often in a compact design for the tight space in the bumper. For use on public roads, they must be approved for the specific vehicle.
LED fog light bulbs
The most common bases in fog lights are H11, H8 and H16. They look alike but differ in wattage and in the locating tab on the base, so they cannot simply be swapped for one another. Older cars and auxiliary lamps use the H3 base, while some Japanese and American models use H1, HB4 (9006) or H10. You can find the right type in the owner's manual or on the original bulb. The rear fog light usually takes a different bulb, most often P21W.
An important choice is the light colour. White light of around 6000 K matches LED headlights and looks modern. Many drivers find yellow light of around 3000 K less dazzling and higher in contrast in fog, rain and snow. There are also dual-colour bulbs that switch between white and yellow when you briefly turn the lights off and on again. The regulations allow both white and selective yellow for front fog lights.
Fog lights sit low in the bumper, where there is often little space behind the lamp and access is frequently only through the wheel arch liner or the undertray. That is why it pays to check the length of the LED bulb and the type of cooling. A passive heat sink without a fan is shorter and copes better with dust and moisture, while a fan removes heat more efficiently. After fitting, seals and dust covers should sit properly so that no water gets into the lamp.
Fog lights have a wide, flat beam with a sharp upper cut-off, which shines beneath the fog and does not reflect back into the driver's eyes. For an LED bulb to keep this beam pattern, its chips must sit in the same position as the filament of the halogen bulb. On cars that monitor current draw, a CANbus-compatible version prevents error messages or flickering.
For use on public roads, an LED replacement in the fog light must have approval for the specific vehicle; otherwise it is intended for off-road use. Front fog lights should only be switched on when visibility is reduced, for example in fog, heavy rain or snow, as in clear weather they can dazzle other road users. After replacing the bulbs, check that both lights shine with the same colour and brightness.