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external display problem

I have a 13" macbook pro 2016 touch-bar running Mojave 10.14.1.

Processor: 3.3 GHz Intel Core i7

Memory: 16 GB 2133 MHz LPDDR3

Graphics: Intel Iris Graphics 550 1536 MBMy external display

I use an external display as an extended screen for work. Sometimes my mac boots up normally with the external display and then turns off suddenly and sometimes I boot up my mac and the external display does not boot up. It is very random and frustrating. I've tried multiple ways to get a permanent fix to no avail. Booting up, down, disconnecting, pressing Shift+Control+Option+Power for 10 seconds, then Power button. Nothing. I have normally been able to get it to work only after I have fiddled around multiple times which takes lots of time. I'd appreciate any advice to get a permanent fix. Thanks.

MacBook Pro TouchBar and Touch ID, macOS Mojave (10.14.1)

Posted on Nov 12, 2018 5:53 PM

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Question marked as Best reply

Posted on Nov 13, 2018 6:46 PM

to get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, no data will be sent to the display.


This query is only sent at certain times:

• at startup

• at wake from sleep

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• on invoking Option-(Detect Display) button in Displays preferences


so try doing some of those things and see if the display comes alive.


Modern Displays with multiple ports are sometimes busy scanning the other ports, looking for an input, and miss the query from the Mac. They need to pay attention to the port you are actually using, or they will miss the query.


Some displays have On-Screen Display settings that can be used to tell the display a computer is attached on a certain port, or a certain port should be highest priority. Changing those may make your display more responsive.

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3 replies
Question marked as Best reply

Nov 13, 2018 6:46 PM in response to StefanieLE

to get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, no data will be sent to the display.


This query is only sent at certain times:

• at startup

• at wake from sleep

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• on invoking Option-(Detect Display) button in Displays preferences


so try doing some of those things and see if the display comes alive.


Modern Displays with multiple ports are sometimes busy scanning the other ports, looking for an input, and miss the query from the Mac. They need to pay attention to the port you are actually using, or they will miss the query.


Some displays have On-Screen Display settings that can be used to tell the display a computer is attached on a certain port, or a certain port should be highest priority. Changing those may make your display more responsive.

external display problem

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