Dimmer Switch
WARNING: This page is about a different car, the 2017 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
The dimmer switch is a momentary contact switch that is integral to the headlamp switch. The headlamp switch is monitored by the BCM. When the dimmer up or dimmer down button is pressed, the signal from the BCM is routed to ground indicating a request to increase or decrease the illumination brightness level.