10-04-2012 11:51 AM
I have a T420 and its fn+brightness control key does not work. Its working is ery sporadic,... sometimes it does and sometimes it does not. When it does not wrk I try to do it by setting the power management > screen brightness but even that does not work. Seems like either the control is anywhere else or the switch is not working. ( A hardware problem)
I read some earlier posts but that was relating to system issues after windows updates / graphics ... but my issue is sporadic and it is there from day 1.
Solved! Go to Solution.
11-06-2012 11:51 PM
Welcome to the community.
Sometime due to software compatibility, the Fn+brightness control key is not working. I would suggest you to please update the Power Manager software and graphics driver of your notebook from the below mentioned web link.
After this, please restart the notebook and check if the issue resolved.
11-07-2012 12:18 AM
I think I had the same problem when I formated my machine. I used Lenovo Solutions Center to update my graphic driver & power manager softwares and all is working correctly. I believe the solution provided by Sameer will work.
All the best.
08-14-2013 01:08 PM
I had the same problem with my T420s when I closed the lid to the laptop while the laptop was being shut down. The Fn+brightness keys stopped working and the machine would no longer go to sleep when I closed the lid.
The solution was to manually put the machine to sleep and then wake it up. After that the missing functionality was restored. You can manually put it to sleep in Windows 7 by going Start >> Shut down arrow >> Sleep.
03-14-2014 12:23 PM
Problem is intermittent. Problem occurs when closing the lid before computer goes to sleep. This happens when you have the lid-closure set to "sleep", or if you sleep it manually (Fn+F4) and close the lid before it finishes (moon lights up on case top).
Rebooting solves the problem.
Some people have luck when changing/upgrading/downgrading the display driver. Or uninstalling/reinstalling the Hotkey program.
Workaround for me seems to be: set closing the lid to "do nothing"; if you get caught without brightness, close and re-open the lid. Voila. It's nice when it works.
Found this on this thread, which also has other suggestions: