The fog light bulbs are the bulbs that are located underneath the headlights, and provide the illumination for the fog lights. They are usually high intensity bulbs, sometimes tinted yellow, and are designed to help increase visibility. The light provided by the fog/driving lights make the vehicle easier to see for other drivers and make the edges of the road easier to see during adverse conditions, such as heavy rain or dense fog. As the bulbs are what provide the illumination for the fog lights, when they fail or have an issue, they can leave the vehicle without functioning fog lights. Usually a bad or failing fog light bulb will produce a few symptoms that can alert the driver of an issue.
Fog lights are dim or flickering
One of the most common symptoms of a problem with the fog light bulbs are fog lights that are dim or flickering. If the fog lights begin to suddenly shine more dimly than normal or flicker when they are turned on, then that could be a symptom that the light bulbs are worn. Aside from not providing proper illumination, usually dim or flickering bulbs are also approaching the end of their service life and likely only have a short time before they fail completely.
Fog lights do not turn on
Another symptom of a problem with the fog/driving light bulbs are fog/driving lights that do not turn on. If the bulbs break or the filament wears out for whatever reason, it will leave the fog lights without functioning bulbs. Broken or non-functional bulbs will have to be replaced to restore functionality to the fog lights.
Fog light bulbs are the same as any other bulbs. While fog lights are only utilized during specific driving conditions, they are an important feature that can increase safety. If you suspect that your fog/driving light bulbs may be out, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if your car will need a fog/driving light bulb replacement.
This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing Fog/Driving Light Bulb and was authored by Eduardo Ruelas.