Why Does My LCD Screen Become Dim or Sometimes Flicker or Brighten Intermittently

Why does my LCD screen intermittently dim or flicker?

Dell has received reports from laptop users and users of some desktop LCD displays about how the LCD display would randomly dim or brighten or occasionally flicker for no apparent reason.

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.

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Ambient Light Sensors

Ambient light sensors are devices that detect the amount of available light 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 1/2 that 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 in the LCD bezel of a Latitude E6410 (Figure 1).

Figure 1: Location of the ambient light sensor

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 (Figure 2).

Figure 2: BIOS settings for the ambient light sensor

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 (Figure 3).

Figure 3: On-screen display options for ambient light sensor settings