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Yosemite does not recognize external displays...

I will bring this up again since I know a lot of people are having this issue, myself included, and the previous forum indicated that the problem was not solved although it as marked as unsolved 😟


Can anybody offer some help? Ever since I upgraded to Yosemite, my Macbook Pro (15'' 2013) won't connect to any external monitor, projector, etc. Not OK. IF you haven't upgraded to Yosemite yet, DO NOT UPGRADE!!!!!

MacBook Pro with Retina display, OS X Yosemite (10.10)

Posted on Nov 11, 2014 9:02 AM

Reply
8 replies

Nov 13, 2014 6:34 AM in response to SS7886247

Hi SS7886247,


I see that you are having issues with your external display since the update to Yosemite. I would like to suggest that you perform a PRAM reset to see if this troubleshooting step affects the issue:


OS X Yosemite: Reset your computer’s PRAM

http://support.apple.com/kb/PH18761


There are some further troubleshooting steps found in this article as well:


Apple computers: Troubleshooting issues with video on internal or external displays - Apple Support

http://support.apple.com/us-en/HT201177


Thanks for coming to the Apple Support Communities!


Regards,


Braden

Nov 13, 2014 9:54 AM in response to wiherek

Hi Wiherek,


After I installed the PRAM I unplugged the cable from the adapter, and tried again - to no avail. I have done this several times, and restarted my computer several times and tried again.

I also started up my computer in safe mode and played with the display settings while connected with my computer, again to no avail.

There is no Thunderbolt 1.2 Firmware update available for me (I have searched in App Store and nothing comes up).

I'm not really sure what "permissions problem in displaypolicyd" means, so I went back and read the other threads and still don't know how to do this (the threads are above my computer competency).... do I type something somewhere? Do I just run disk utility to check my hard drive?

Nov 13, 2014 1:17 PM in response to SS7886247

Hi again,


you don't install PRAM, you have to reset it, the instructions are here OS X Mavericks: Reset your computer’s PRAM


as for the displaypolicyd, you need to type this into the terminal:


sudo diskutil repairPermissions /


and for the update, there is no such app, but the update is in the tab updates in AppStore, under Software Updates, just click 'More'

Jan 17, 2015 6:50 PM in response to wiherek

Has there been any resolution to these issues? I just upgraded a late '12 Mac Mini to Yosemite and am now also having similar difficulties, utilizing TWO Video Output options simultaneously. With 10.8.5 I was using my Thunderbolt port to adapt to VGA which goes to a Stardom KVM and then to a professional 1920x1080 monitor, while at the same time utilizing the HDMI port to connect to an AJA HA5 convertor (which adapted that video signal to SDI).. Everything worked seamlessly before this upgrade. Using exactly the same hardware my current problem is that my Mini(s) now fails to correctly recognize my monitor that is down the line from the Thunderbolt to VGA adaptor. That monitor now only gets recognized at some pathetically useless lower resolution, while the HDMI video Out seems to work just fine. In fact, the HDMI out is what the Mini now prefers. WHY??? I likely am missing something, I know.... The Displays preferences is sheer misery to navigate between the two and I have thus far failed to get the two monitors (well, one is actually an SDI router with multiple monitors down the line... and that is from the HDMI Out, which gets converted) to work the same way twice after a re-start. I spent a few hours feeling helpless today. Tomorrow I will do the VRAM reset (forgot to do that today), but I am not so hopeful. Anyone?

Apr 11, 2016 4:37 PM in response to ddscott57

This worked for me when my MacBook Air Mid 2013 El Capitan wouldn't connect to my Epson 4650 projector via VGA adapted to Mini DisplayPort.

Unplug from the projector, go to "System Preferences>Displays>Color"...Find your Projector (might work with monitors also) in the"Display profile" list and delete it.

If built in display color goes wonkie select the top profile, mine was " Color LCD"- or create a new one via the "Calibrate..." button.

Reconnected to my projector and it was recognized.

Yosemite does not recognize external displays...

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