Auto brightness issue

[Khaled Mahmoud1]

When I'm in a light room the screen goes brighter but if I walk into a darker room, the screen doesn't dim unless I lock and then unlock the screen.

Anyone else having similar issues?

I figured something the screen will dim only when I put the phone in horizontal position not when I'm holding it in my hands.

 

[Tim1954]

Dial *#0*#" to get into service mode and you can test that hardware.
Be sure you don't have a phone case that covers the sensor...