Problem with the brightness of the screen--reverse dimming???


New Member
I'm having a problem with my screen brightness setting. I'm currently using a (very old) dell latitude e6400 with Windows 7 while my normal laptop is being repaired. The battery is shot, so it only runs for about 30 seconds without being plugged in. A few days ago, the screen went extremely dim for no reason. I changed the brightness setting, the power plan, adjusted absolutely everything I could, and nothing helped. Its about as dim as the lowest brightness setting would usually be, and yet all of the computer settings say it is at full brightness. I figured it was just an old, broken computer, and Id just have to deal until my regular one is fixed. Then today I unplugged it, and all of a sudden it was bright again! It turns out that when it is unplugged, the brightness works just fine! I have no idea what is happening or how to fix it. Its also not tat the power plan is set to be dimmer when the computer is plugged in, I checked that and it didnt help. Any suggestions? Or is this computer just a lost cause?
(Also, I apologize for any spelling/grammar errors, a few keys on this keyboard decide not to work sometimes including te apostrophe)


Noob Whisperer
Have you tried removing the battery completely?
Most will run off power only with the battery missing, some will not.
Just to test and see if that makes a difference.

Another thing you might try if you haven't already is the hardware keys. Usually a combination of the Fn (function) key and one of the top row Fkeys somewhere around the middle of the row you should see two, one for raising and one for lowering screen brightness.


Senior Member
Reverse dimming is common when the ambient light sensor for the monitor fails. Look for a setting to disable adjusting the monitor brightness for ambient light.


Extraordinary Member
Premium Supporter
One thing is, you most probably have at least two settings for monitor: Windows, and your video card provider i.e. either ATI or NVidia. These may collide.

What I would do is, uninstall ATI or NVidia drivers, with everything. The job may best be done with Revo Uninstaller, get rid of everything = advanced mode. Reboot, check what Windows does.

At least with NVidia, older drivers quite often work better than latest ones. It's a sort of trial and error. The use of the original installation disc for your Mobo / video card could be a start point. Start from the beginning, proceed towards end.


Senior Member
As you have stated there are settings in the POWER section in which you can choose how the screen is supposed to react on battery, vs on A/C power. Additionally there sub settings on what happens when on when the battery runs down a certain percentage.

Since you say the battery is BAD. First thing I'd do is to REMOVE the battery, go into settings and "reset" everything. Then do a COLD, not warm reboot or two.

Another thing that may be occurring (which is highly likely) is the cabling (display to main body) within the laptop being going BAD, and or bad lamps or inverter board.

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