Mercedes-Benz S400 Fog Light Relay Replacement at your home or office.

What is the Fog Light Relay all about?

Your fog lights don’t need to be on if the headlights aren’t on. For that reason, a fog light relay is used. The fog light relay acts as a switch, enabling the fog lights to come on only when certain criteria are satisfied. Typically, fog lights do not come on when the high beam headlights are on either. The relay directs power to the fog lights only when the switch is on and the right lighting circuits are on. The use of a relay means a low voltage fog light switch can be used. If the full voltage of the fog lights runs through a switch, the switch will become very hot and overload.