System Operation - Exterior Auto-Dimming
WARNING: This page is about a different car, the 2018 Lincoln Navigator. However, it is still accessible from the selected car via links, so may be relevant.
When bright light is detected from behind the vehicle during nighttime conditions, the interior auto-dimming mirror supplies voltage and ground to electronically darken the LH exterior mirror glass.
To provide increased visibility when backing up, the LH exterior mirror glass automatically returns to a high reflectance mode whenever the vehicle in REVERSE, regardless of exterior lighting conditions.