My display brightness will not change, how can I fix it?
Display brightness is influenced both by the brightness controls and the display brightness itself. An inability to control the brightness may be caused by either faulty controls not generating brightness changes, or by a lack of control off the displays backlight.
To analyse faulty keyboard controls see the Hotkeys/Troubleshooting.
To analyse faulty backlight control see the Kernel/Debugging/Backlight.