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El Capitan does not detect my external display

After upgrading to El Capitan on my MacBookPro (2015), my external display (27" Dell) is not being detected anymore.

I tried the Thunderbolt and HDMI ports, but makes no difference.

Also tried to re-detect the display (Settings -> Displays -> hold 'Option' -> 'Detect Displays') - but that does not result in a detected monitor.

Also tried to remove the power from the monitor, wait 1 minute and put the power plug back in. Also nothing.

Tried a fresh reboot of the Mac, again nothing.

Any ideas for me to try?

Thank you.

MacBook Pro with Retina display, OS X El Capitan (10.11), null

Posted on Oct 2, 2015 3:19 AM

Best reply

appenz

Level 1

10 points

Posted on Oct 2, 2015 10:16 AM

I have the identical problem. MacBook Pro (Retina, 15-inch, Mid 2014), external Dell display. Before El Capitan (10.11) it was detected reliably.

I tried:

- Manual "Detect Displays" in Settings does not detect it either.

- Power cycle monitor

- Use HDMI vs Thunderbolt

- Reboot

I found that I have the identical problem with a projector in a conference room, thus it doesn't appear to be Dell specific. Any help would be highly appreciated.

Guido

Edit: There are numerous bug reports in other forums of the same issue, but no resolution yet.

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47 replies

blouve

Level 1

4 points

Jul 6, 2016 2:03 AM in response to appenz

Apple recommended this answer, but it does not work for me. Apple -- are there other fixes that are recommended?

May 26, 2017 4:32 AM in response to castor3

Thanks for this. I got the app and adjusted the settings on my external monitor and so far it seems to work!

El Capitan does not detect my external display