Fog Lights

Fog lights are used with other vehicle lighting in poor weather such as thick fog, driving rain, or blowing snow. Because fog is made up of water droplets suspended in the air, it can reflect headlights back into the driver’s eyes at night. In such conditions, fog lights can help drivers see farther ahead and illuminate the road’s edges at reasonable speeds. They are used with park lights and low beam headlights but not with high beams.

FIGURE 39-24
Vehicle with factory fog lights.

Most older fog lights have yellow-colored reflectors, although more recently, white fog lights have become more widely used because yellow lenses reduce fog light brilliance by about 30%. Fog lights typically use quartz halogen bulbs and are available in different shapes and sizes. Fog lights are usually mounted lower than headlights and tend to be aimed straight forward and low Figure 39-24. Fog light lenses have a sharp cutoff pattern so that most of the light projected remains below the driver’s eye level.

Fog lights are typically wired with a relay and circuit breaker. The method of connection of fog lights will depend on local regulations. They may be wired to work only with park lights and to turn off when headlights are used or to work when high beams are used. The BCM normally controls the function of the fog lights if they are installed as original equipment.