F4 Function Key LED Is Always on Even If Pressed on Some Latitude Systems

F4 Function key LED is always on even if pressed within Windows

Some users have reported that the F4 key is constantly lit once the system has booted into Windows. Pressing the key has no effect.

The issue was initially reported on Latitude E7270 and E7470 computers, but is also present on other computers such as E5450/5450, E5250/5250, E5550/5550 so on that have the same F4 key with LED.

Figure 1

On some Latitude systems, the F4 key is used to mute the integrated microphone (Figure 1). However if the Microphone is disabled in the BIOS the light will remain on after the system has booted into the Windows operating system.

This is working as designed, and the light remains on as an indication that it has been disabled in the system BIOS. To restore the functionality of the F4 key, re-enable the microphone in the BIOS.

In the BIOS of some systems like the E7270 or E7470 the microphone is enabled under "System Configuration" and "Audio" (Figure 2).

Figure 2

In the BIOS of some systems like the E5450 the microphone is enabled under "System Configuration" and "Miscellaneous Devices" (see Figure 3).

Figure 3