Fix for Dell laptop display brightness randomly changing

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If you have a Dell laptop, it might have a built-in “feature” called Ambient Light Sensor (I put “feature” in quotation marks intentionally). This is not really a widely advertised function so a lot of people don’t know about it. In fact, I personally was not aware of it until my friend Bob did some research and discovered it. Love it when the client comes up with the solution, then tells me about it. Thanks Bob!

Ambient Light Sensor


What is the Ambient Light Sensor?

The ALS is something that Dell has built in to some of their laptops (I’m not sure all Dells have this). Basically, it’s a way for the laptop’s screen brightness to adjust based on how much light is in the room. So if the laptop is powered on, and you turn the lights up or down in the room, you will probably see the laptop’s screen get darker or brighter.

I guess some people might like it, but for most people, it’s annoying to have the screen brightness always changing even though you are not actually trying to adjust the brightness level. And for those that don’t know about this special “feature” it might even appear that the screen is defective. Nope, it’s just a computer manufacturer thinking they would offer something new and clever, but in reality it’s just something most people would prefer to turn off.

Here’s how you turn off the Ambient Light Sensor:

1. Find the “Function” key on the keyboard. It will be somewhere in the lower left area, usually between Ctrl and the Windows key:

Function key


2. Hold down the “Function” key and tap the left arrow key.

Pretty easy, right? Just a matter of knowing what keys to use, then the problem is solved.

Turns out there are a few other things you can do on your Dell laptop with that handy little Function key. In the list below, the Function key is abbreviated “Fn”. And remember, these might not work on all Dell laptops.

Fn + F1 puts your computer to sleep

Fn + F2 toggles the battery charging process on and off

Fn + F3 shows status of the battery

Fn + F8 toggles between screens if you have an external monitor connected

Fn + F11 copies a screenshot to the clipboard

Fn + Up Arrow key increases screen brightness

Fn + Down Arrow key decreases screen brightness

Fn + Right Arrow key adjusts brightness of the backlit keyboard (optional)

Fn + Left Arrow key toggles Ambient Light Sensor on and off (as described above)

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Suzanne van der Merwe
September 7th, 2015

I don’t have a Dell, but I have the Fn key just as you show us.
I did what you said and will have to see if it is working , getting bright and staying bright–I went through the list of combinations you give us and I am using that too,
This is a very appropriate thing to do.
Thanks for showing us so many doable improvements!


Scott Johnson
September 7th, 2015

Suzanne, I cannot say what effect those things will have on computers that are not Dell – you may or may not want to experiment with that.

September 9th, 2015

This came at the perfect time as this issue just arose within the last 2 days on my Dell. Look forward to giving this a try.

Scott Johnson
September 9th, 2015

Cool, Jon! Hope it solves the problem.

September 24th, 2015

Thank you so much for this Scott!!! I just bought a new Dell and at first I thought I was going nuts and if I wasn’t it was quickly driving me there. Glad to know it was a easy fix. Haha Once again you have saved the day 🙂