External monitor won't work when I unplug the power to my MacBook Pro?!

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External monitor won't work when I unplug the power to my MacBook Pro?!

I have a 2016 MacBook Pro with two Thunderbolt 3 ports. I have one port connected to power and the other to an external monitor. But something weird happens when I try to unplug the power and use that port for something else. Even though the external monitor is still connected, as soon as I disconnect the power cable, the monitor won't work! It does work if I have the laptop open, but if I try to use the monitor as my only screen (with the laptop closed) it won't work. This makes no sense! Any ideas, anyone?

MacBook Pro 13″, macOS 10.14

Posted on Dec 23, 2020 7:53 AM

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Answer 1

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neuroanatomist

Level 9

50,359 points

Dec 23, 2020 9:33 AM in response to bunny_mac78

That is normal. To work in clamshell mode (lid closed) you need:

External display
External keyboard
External trackpad/mouse
AC power

See: Use your Mac notebook computer in closed-display mode with an external display - Apple Support

You may want to consider a hub/dock that provides power and display connection over a single TB3 cable. Docks from Brydge, OWC and Elgato work well with Macs.

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External monitor won't work when I unplug the power to my MacBook Pro?!

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