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darrenVpV Author

Level 1

17 points

External display won't wake up from sleep

I have a 2017 iMac Retina 4k with an LG Ultrafine 21.5" external display connected using thunderbolt 3 cable (no adapters). Other folks in my office have this working just fine with 2017 macbooks.

The issue Im having is consistent and as follows:

The external LG display works except that it will not wake up from sleep when the iMac does. On top of this, the mouse and other UI components stutter when being moved. Unplugging and plugging back in the thunderbolt cable connecting the display fixes this and resets the displays and turns on the LG.

Its obviously frustrating to have to do this every time the mac needs to wake up from sleep or alternatively setting the mac to never sleep. I've tried various changes to the Energy Saver settings to no avail.

Posted on Oct 17, 2017 7:17 AM

Best reply

Stubbornthinker

Level 1

9 points

Posted on Nov 23, 2017 8:51 PM

I have the same issue with the 5K iMac and 27 inch LG Ultrafine. In another discussion someone wrote the following:

Just found the solution for this, the screen LG has is own power source and when you have it connected to the mac he is charging the mac through the USB-C, so if you have another cable (power adaptor) plugged in the screen won't be able to turn on after sleep because power priority will go to the power adapter, so the solution is simple if you have your macbook pro 2016 connected to the screen unplug the power cord because it will charge directly from the screen.

It seems from responses this fixed the issue for the MacBooks. Has anyone found a workaround or solution for the desktop IMac? It is frustrating having to unplug and replug in the cords. Thanks for any advice.

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External display won't wake up from sleep