Windows 10: Laptop brightness stuck at 100% when plugging in an external monitor

Laptop: ASUS - ROG Zephyrus G14

Operating System: Windows 10 Version 2004 Build 19041.264


Issue: When I connect an external monitor to my laptop using an HDMI cable, the laptop's screen's brightness is automatically set to the maximum. Adjusting the brightness with the slider in the taskbar panel does nothing. The numbers go up and down but the laptop's brightness doesn't change. Adjusting the brightness with the keyboard doesn't do anything. I also tried changing it through commands in PowerShell but that also didn't work.


All drivers are updated to their newest versions. I also tried rolling back the AMD Radeon Graphics driver under the Display Adapters in the the Device Manager and that didn't fix anything. I also tried uninstalling/reinstalling the drivers for the laptop's built-in display shows up as Generic PnP Monitor but that does nothing.


Other things I have tried:

• changing the Power Plan for the laptop but that also did not do anything.
• making changes to the registry which did not do anything.
• uninstalling the hidden Generic PnP Monitor drivers

Here's a screenshot of what my Device Manager looks like if that helps at all




This ONLY happens when I plug in an external monitor. I tried two different ones and I get the same problem with both. As soon as I unplug one, I can change the brightness like normal. That leads me to believe the issue occurs with whatever piece of hardware/software deals with detecting input from the HDMI port. But I have no idea other than that.


I have been trying to fix this for hours and have gotten nowhere. I am losing my mind and am so close to just returning this laptop. I can't work like this

:)

 

Can't change brightness on Windows 10 when plugged into a monitor

Hi Daniel,

This is Wil, one of the independent advisor and an expert with Windows 10.

I understand your concern about changing the brightness of Windows 10 when plugged into a monitor.

Like what you mentioned that this issue only happens when you close the lid of the laptop. Actually the brightness control within the operating system would only work on the laptop's display. As for the external monitors that you attached on your laptop they
have their own physical controls usually on the bezels or frame of the monitor. From there, you can control the brightness of each monitor.

I hope my suggestions help you. If you need further assistance please do reply back and I will respond as quickly as possible. Have a nice day.

Thanks,

Wilfred P.

Independent Advisor

 

External Monitor Brightness Resets when turned off

I recently got an external monitor, Lenovo L24q-20, which I use with my HP Envy Laptop. The brightness of the external monitor is controlled with buttons on the monitor, and is by default set to 80/100. This is a bit too bright for me so I set it down to 50/100, and all is well. However, when my laptop/the monitor go to sleep, when I wake my computer back up the value has reset to 80/100. Does anyone know why this is and any fixes I could try. I've restarted the computer and updated the drivers so far.

 

monitor brightness?

Hi Tom,

To change your Windows 10 monitor brightness, we suggest that you follow the steps below:

• Click the Windows logo; then, search for Control Panel.
• Select Hardware and Sound.
• Choose Power Options.
• On the next screen you should see brightness slider at the bottom of the Control Panel window.
  

We would appreciate it if you could get back to us and provide us your feedback.