Dimmer Switch
WARNING: This page is about a different car, the 2018 Ford Focus. However, it is still accessible from the selected car via links, so may be relevant.
The illumination dimmer switch is a momentary contact switch that is integral to the headlamp switch. When the illumination dimmer switch is pressed, Dim up or Dim down, the requested illumination level is sent to the BCM over a LIN circuit.