XPS 9550 - Function keys cannot adjust brightness on battery, but can adjust everywhere else (action center, power settings)
Using the laptop on battery, when I press on F11-12, the brightness meter is shown on the upper left like usual, but it won't move up or down. Yet I think it's strange that all other places I can adjust brightness are fine, and especially strange that everything is working totally fine on AC power.
I tried uninstalling the Generic PnP monitor and reinstalling, but to no results. Also, both my power settings on battery and on power indicate no adaptive brightness.
RE: XPS 9550 - Function keys cannot adjust brightness on battery, but can adjust everywhere else (action center, power settings)
The fact that it works on AC adapter means that this is strictly a software driver issue or operating system issue. Not a laptop hardware issue. Reinstall the chipset drivers (7) one at a time, restarting after each one. Then reinstall the Dell Command Power Manager, restart and retest.