Screen on E4200 dim and then brighens on its own

I have owned a Dell E4200 for about 1 month. I purchased this E4200 as a refurbished unit from the Dell Outlet. Overall, I am pretty happy with my
E4200, I really like the backlit keyboard, weight/size, solid state drive..price I paid...etc.

But, the screen on my E4200 dims and brightens and then brightens and dims on its own...with no change in the surrounding environment lighting. For example, I will be sitting with the laptop and all of a sudden the screen will start dimming...and it stays dim for 3-5? seconds...I can still see everything...but screen appears to have lost about 20-40%? of its brightness...usually the screen will then brighten back to where it was...this cycle will then repeat 2-3 times...this might happen 5-6 times per day...other days it might happen only once or twice ...sometimes the screen brightens on its own...and them dims back...

This screen brightening /dimming...is not a huge deal...I can still use the laptop fine while this happens...but it is a bit annoying...and I woulod like to know if there may be something wromng with the laptop/screen...

Any ideas or input? Is my screen defective? Should I contact Dell ?

 

Does this occur with the ambient light sensor disabled?

 

No, my friend, your screen is not defective but it does use something that Dell calls the Ambient Light Sensor. The ALS is supposed to help us but some times technology hinders us instead. You can turn ALS off by pressing the FN (Function) and the Left Arrow/Cursor keys together. You can also adjust the brightness of your display manually by using the FN key +Up/Down Arrow key combinations.

I hope this helps.

 

if it does it when you don't move the system try with an external mouse and keyboard and don't even bump the power adapter if it does it without you touching it you can update all drivers then contact Dell

 

Thanks for the replies. The ALS was enabled. For now, I have used the Dell Control Point software and turned off the ALS. With the ALS enabled the screen brightness was changing on its own...even when the laptop was not moved and external lighting conditions did not change. I might try and update all the drivers and retest.

 

The ALS worked really well on the old Lattitude D8xx series.
On the new stuff...not so well. It is unusable on my M6400 - like you I find that the screen dims and brightens of its own accord.