The electric rearview mirror automatically controls the glare from the headlights of the car behind you in nighttime or low light driving conditions.
When the engine is running, the glare is automatically controlled by the sensor mounted in the rearview mirror. The sensor detects the light level around the vehicle, and automatically adjusts to control the headlight glare from vehicles behind you.
Whenever the shift lever is placed in R (Reverse), the mirror will automatically go to the brightest setting to improve the driver’s view behind the vehicle.

To operate the electric rearview mirror:
CAUTION
When cleaning the mirror, use a paper towel or similar material dampened with glass cleaner. Do not spray glass cleaner directly on the mirror as that may cause the liquid cleaner to enter the mirror housing and damage the rearview mirror.
Day/Night rearview mirror (if equipped)
Blue Link® center (if equipped)Hyundai Tucson (LM) 2010-2015 Owners Manual: Mode selection
The mode selection button controls the direction of the air flow through the
ventilation system.
The air flow outlet port is converted as follows:
Face-Level (B, D)
Air flow is directed toward the upper body and face. Additionally, each outlet
can be controlled to direct the air disch ...
Hyundai Tucson (LM) 2010-2015 Service Manual: Underdrive Brake Control Solenoid Valve(UD/B_VFS) Specifications
Specifications
Direct control VFS[UD/B]
x Control type : Normal high type
Control Pressure kpa (kgf/cmx, psi)500.14 ~ 9.81(5.1 ~ 0.1, 72.54 ~ 1.42)Current value(mA)50 ~ 850 Internal resistance(x)5.1
...