Hello, Mr. Eagle.
There are two typical issues that occur which may be making your screen light dim.
(1) Your screen may be disabled. In this case, press the buttons fn+f7 in order to enable/disable screen lock.
(2) Check your battery life. After plugging in your charging cord to a fully functional wall outlet, wait a couple of minutes for your computer to reboot. Once the laptop reboots, the screen light should be restored.