Why Does My LCD Screen Dim, Flicker, or Brighten

Why does my screen keep dimming, flickering, or brightening?

Dell has received reports from laptop users and users of some desktop LCD displays about a randomly dimming screen. This may also be seen as the LCD screen randomly dims and brightens, or even flickers.

Research into these incidents most often leads to the ambient light sensor (ALS) as the cause for the change in appearance. Read on for more information about how to troubleshoot the ambient light sensor.

How ambient light sensors can affect the LCD screen

Ambient light sensors are devices that detect the amount of light available in the workspace. They automatically dim or brighten the LCD display based on the amount of light that the computer is encountering. Most newer automobiles have similar technology to brighten or dim the dashboard lights. Generally, complaints about ambient light sensors on LCDs are traced to the light source intensity changing rapidly and the LCD attempting to adjust to the changes. For example, partly cloudy days, curtains blowing in a breeze, and even a failing fluorescent lamp can affect the ambient light sensor.

Here are some tips to help deal with flickering or dim LCD issues related to the function of the ambient light sensor.

• If the computer is located near a window on a partly cloudy day, closing the curtains or blinds should stop any issues caused by changing cloud cover.
• If a computer is being used on battery power, and the LCD is too dim, then the brightness may be adjusted with the Fn Key keystrokes for your computer. Portable LCDs are set to full brightness on AC power by default, and to less than half that when running on battery to save power. On battery, the ambient light sensor is typically disabled.
• You may choose to disable the ambient light sensor if you cannot control changing light situations (working outdoors, and so on). On most laptops, this function is controlled in the BIOS (ambient light sensor enabled or disabled).

On desktop LCDs equipped with an ambient light sensor, the on-screen display controls allow you to enable or disable the sensor. Often, the ambient light sensor cannot be seen on the display bezel on a desktop LCD. In the image below, you can see the ambient light sensor next to the camera at the top of the LCD bezel of a Latitude E6410.

Basic Input Output System (BIOS) settings for an ambient light sensor vary between BIOS designs. Generally, they are similar to the ones below on a Latitude E6410.

The on-screen display (OSD) options for an ambient light sensor equipped desktop LCD display (Dell G2210, for example) may look like the image below.