Sierra broke external VGA monitor connection

Discussion in 'macOS Sierra (10.12)' started by Joseph Farrugia, Oct 11, 2016.

  1. Joseph Farrugia macrumors regular

    Jul 31, 2011
    Malta (EU)
    Posting here as an FYI, as well as a query for help if someone has a solution.

    Sierra broke my external VGA monitor connection; it's mDP->VGA adapter.

    I'm booting Sierra off an external HDD connected vis USB to my late 2013 15" rMBP, & I have also a 27" ACD connected.

    When I boot from Yosemite, from my internal SSD on my rMBP, all 3 displays work fine; the rMBP recognizes both the ACD as well as my old Viewsonic display connected via a mDP to VGA adapter.

    Trued SMC & PRAM resets, disconecting & reconnecting, rebooting, detecting displays by pressing the Option key, etc no avail.

    The fact that all works OK (quasi-OK: my external Viewsonic is only recognized in lower rez than its actual 1680x1050) on Yosemite means it's a Sierra problem, not a rMBP problem, right?

    Thanks to all who participate in these forums, I learnt so much from you guys, appreciated!
  2. i3_theanswer, Oct 12, 2016
    Last edited: Oct 12, 2016

    i3_theanswer macrumors newbie


    Oct 12, 2016
    Had the same problem. Read in another forum that Sierra might have disabled 3rd party adapters. I tested and can verify it is true, at least for now. I tried 2 3rd party mDP->VGA adapters that worked before Sierra, and MacBook screen flashed on plug-in but the monitor was not detected by the MBPR (late-2013 15in). Asked a friend for an Apple branded adapter and it worked right away. It is frustrating, hope Apple will be generous enough to allow 3rd party adapter for use again.

  3. Joseph Farrugia thread starter macrumors regular

    Jul 31, 2011
    Malta (EU)
    Thanks for your input; so I understand that the Apple branded mDP-VGA adapter works with Sierra?

    Pity 3rd party ones don't, it's a deal breaker for me because as an educator I often have to connect to a projector, which almost all use a VGA connection; & might need to use a 3rd party connector.

    I'm seriously thinking of staying with Yosemite even though Apple purposefully made the newer & better Safari upgrades (including a better zoom feature, & no the cc hacks to not work correctly) available only in Sierra.

    Apple used to be "it just works", what a shame it's no longer the case.
  4. mrsoonersky macrumors newbie

    Mar 10, 2011
    I am experiencing this same issue, except it's a MacBook Pro Mid 2012, with a direct mini display port to display port cable. If the MacBook puts the display to sleep, then the external monitor will never come back on until I shut down the computer. A reboot doesn't fix it. This started with 10.12.1 was installed. Worked fine on 10.12.

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3 October 11, 2016