[GH-ISSUE #972] Blank screen on my LG 34BK95U monitor - connected to MacBook M1 Max laptop #590

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opened 2026-05-05 06:18:56 -06:00 by gitea-mirror · 2 comments

gitea-mirror commented

2026-05-05 06:18:56 -06:00

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Originally created by @patrickcwtsui on GitHub (Mar 10, 2022).
Original GitHub issue: https://github.com/MonitorControl/MonitorControl/issues/972

Before opening the issue, have you...?

Searched for existing issues
Read through the Monitor-Troubleshooting Wiki
Updated MonitorControl to the latest version (if applicable)

Describe the issue

I have a Thunderbolt-3 (USB-C) connection from my MacBook M1 Max laptop to my LG 34BK95U monitor that I've been using for 5-6 months in clamshell mode with no issues. I found MonitorControl and installed it last night - it worked like a charm! However, when I went to start my system up from sleep, the monitor no longer came up (it was dark). Note, the Display Preferences still shows a connection and I can move my mouse to the external monitor. I just can't see a thing.

I then installed m1ddc and when I typed:
patricktsui@Patricks-MacBook-Pro m1ddc-main % ./m1ddc set luminance 100

I got the following response:
I2C communication failure: (iokit/?) unknown subsystem error

I searched this response but there wasn't much help.

Expected behavior

I guess I was expecting that I could use MonitorControl to control the brightness on my LG 34BK95U monitor in clamshell mode with my MacBook M1 Max laptop but now I can't even use my external monitor.

Anything else?

I'm not sure what else I can offer here - please prompt for resources that I can provide that will help with a solution.

Environment Information (please complete the following information)

- macOS version: 12.2.1
- Mac model: Macbook M1 Max (14") 32GB RAM
- MonitorControl version: 4.0.2 build 6995
- Monitor(s): LG 34BK95U
- Monitor Cable(s)/Connection(s): Thunderbolt 3 (USB-C)
- Apple Silicon/M1 (yes or no): yes

Originally created by @patrickcwtsui on GitHub (Mar 10, 2022). Original GitHub issue: https://github.com/MonitorControl/MonitorControl/issues/972 ### Before opening the issue, have you...? - [X] Searched for existing issues - [X] Read through [the Monitor-Troubleshooting Wiki](https://github.com/MonitorControl/MonitorControl/wiki/Monitor-Troubleshooting) - [X] Updated MonitorControl to the latest version (if applicable) ### Describe the issue I have a Thunderbolt-3 (USB-C) connection from my MacBook M1 Max laptop to my LG 34BK95U monitor that I've been using for 5-6 months in clamshell mode with no issues. I found MonitorControl and installed it last night - it worked like a charm! However, when I went to start my system up from sleep, the monitor no longer came up (it was dark). Note, the Display Preferences still shows a connection and I can move my mouse to the external monitor. I just can't see a thing. I then installed m1ddc and when I typed: patricktsui@Patricks-MacBook-Pro m1ddc-main % ./m1ddc set luminance 100 I got the following response: I2C communication failure: (iokit/?) unknown subsystem error I searched this response but there wasn't much help. ### Expected behavior I guess I was expecting that I could use MonitorControl to control the brightness on my LG 34BK95U monitor in clamshell mode with my MacBook M1 Max laptop but now I can't even use my external monitor. ### Anything else? I'm not sure what else I can offer here - please prompt for resources that I can provide that will help with a solution. ### Environment Information (please complete the following information) ```markdown - macOS version: 12.2.1 - Mac model: Macbook M1 Max (14") 32GB RAM - MonitorControl version: 4.0.2 build 6995 - Monitor(s): LG 34BK95U - Monitor Cable(s)/Connection(s): Thunderbolt 3 (USB-C) - Apple Silicon/M1 (yes or no): yes ```

gitea-mirror closed this issue

2026-05-05 06:18:58 -06:00

gitea-mirror commented

2026-05-05 06:19:01 -06:00

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@patrickcwtsui commented on GitHub (Mar 11, 2022):

I have an update - I pulled the power plug on the monitor and plugged it back in and now it works... kinda. The external display can serve as an extended monitor but will not work in clamshell mode. When I try clamshell mode the system doesn't recognize the monitor and displays the same issues as above.

@patrickcwtsui commented on GitHub (Mar 11, 2022): I have an update - I pulled the power plug on the monitor and plugged it back in and now it works... kinda. The external display can serve as an extended monitor but will not work in clamshell mode. When I try clamshell mode the system doesn't recognize the monitor and displays the same issues as above.

gitea-mirror commented

2026-05-05 06:19:04 -06:00

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Owner

@patrickcwtsui commented on GitHub (Mar 11, 2022):

Ok, I have the fix! Delete these two files:

• /Library/Preferences/com.apple.windowserver.plist
• ~/Library/Preferences/ByHost/com.apple.windowserver.XXXXX.plist

Restart, and you should be good...

@patrickcwtsui commented on GitHub (Mar 11, 2022): Ok, I have the fix! Delete these two files: • /Library/Preferences/com.apple.windowserver.plist • ~/Library/Preferences/ByHost/com.apple.windowserver.XXXXX.plist Restart, and you should be good...