The screens are bit too bright for my taste.
The Gauge dimmer does not do anything to the screens.

How can I dim the screens?

Thanx for helping...

 

Is the light sensor on the head unit intact? It's on the upper left side of the faceplate, right below driver's side heat control buttons. It looks a lot like a reset button on electronic devices and some people have broken it by pushing it in with a pen, hoping that it'll reset the HU. I'm not quite sure how the screen dimming function works or if one even exists so this is mainly an educated guess.