Re: alfa 166 2.5 ICS WONT SWITCH ON
If you have tried everything (including the 'Dark' button) then it is possible that the backlight or the backlight inverter for the LCD screen has blown.
Unfortunately the backlight is a U shaped one and they are not easy to find.
Try this. Wait until it's dark outside and start the car normally. Get a torch or use the light from a mobile phone and shine it just above the screen. If you can faintly see the display then it is more than likely the backlight problem.
Like I say, only after you have tried everything else, might this be the cause.