AUTO Defog Humidity Sensor
WARNING: This page is about a different car, the 2021 Hyundai Kona. However, it is still accessible from the selected car via links, so may be relevant.
The Auto Defog Sensor is installed at the front glass. It monitors the humidity of the glass surface and sends a signal to the A/C Control Module. Then the module curbs and eliminates the moisture at in advance by controlling the intake actuator, A/C, auto defog actuator (Auxiliary DEF actuator), blower motor, and mode actuator.