Fix a Flickering Screen Issue with External Displays After Updating OS X

Jan 4, 2014 - 24 Comments

Fix a flickering not-working external screen problem with Macs

Having recently went through the process of updating a handful of Macs to OS X Mavericks as part of a gifting tech support campaign, several Macs developed an odd flickering display problem that was only visible when an external monitor was connected to the Mac. On an 11″ MacBook Air, the screen flickers with any DVI or VGA display hooked up with the standard Min-iDisplayPort adapter, and displays only a white-black noise screen, like an ancient TV without an antenna. Meanwhile on a newer MacBook Pro, the problem exhibited as external display flickering with anything from DVI connections to HDMI, and with different brand monitors, but the screen would display properly just with a persistent randomized flicker. The video below demonstrates the MacBook Air flickering on and off with a noisy picture:

(Excuse the vertical video formatting, someone didn’t follow this important advice for recording with the iPhone camera!)

Because each of the Macs behaved perfectly normal with external displays prior to the OS X update, and the problem spans between two totally different Macs and with different connection types and even monitor brands, this suggests something went awry during the upgrade process. That’s good news, because that also means the problem was likely not to be simultaneous concurrent hardware failure – a truly rare event that would be even moreso with two unrelated machines failing side by side. Fortunately, a simple SMC reset resolved the problem completely on both Macs, and external displays again worked as they should post-SMC reset.

Resolve Monitor Flickers by Resetting the System Management Controller of a Mac

This is how you reset the SMC on a portable Mac that has a built-in battery (not a removable battery), like a MacBook Air, or new MacBook Pro with Retina display. You can find details for SMC resets on other Macs here, and Apple has directions for other machines here too.

  • Disconnect the external display from the Mac
  • Shut down the Mac so that it is turned OFF (not sleeping)
  • Connect the MagSafe power adapter to the MacBook
  • Using the built-in keyboard on the MacBook, press and hold down the Shift+Control+Option+Power buttons at the same time (see the image below for details) and hold them for about 2 seconds, then release all keys together

These are the keys to press and hold simultaneously on the MacBook Pro / Air keyboard to reset the SMC:

Reset the SMC of a MacBook Air or Retina MacBook Pro

When that is finished, boot the Mac and reconnect the display:

  • Now press the Power button on the keyboard to boot the Mac as usual
  • Wait until the Mac is booted and reconnect the external display

Everything should be working as usual, no more monitor screen flickering, no more noisy screen displays, just the Mac with a normal looking external display.

Beyond display issues, resetting the System Management Controller can also resolve many other problems related to power management and hardware, both that have occurred post system updates or seemingly at random. We’ve covered several other issues like this in the past, including a suddenly missing battery and fans blaring on portable Macs, inability to put a Mac into sleep mode, and fan noise and heat issues that have popped up after installing a system update. Because there is little harm in resetting the SMC beyond losing some simple Energy settings that you can reconfigure within System Preferences, it’s worth trying yourself before taking further steps to resolve hardware problems with any Mac, and it’s actually a common step recommended by Apple Genius staff through phone support, and even at the Genius Bar in an Apple Store.

If you or anyone you know happens to run into the screen flicker issue after an OS X update, try this SMC fix first, it only takes a moment and resolved the problem quickly in these cases, and just may work for you too.

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Posted by: Paul Horowitz in Mac OS X, Troubleshooting

24 Comments

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  1. mcl says:

    Had a camera issue on new Retina MBP. Called AppleCare and was instructed to do this. Resetting solved my problem.

  2. Jason says:

    Rookie photoshop job on the laptop bezel for this article. Just saying.

  3. MickM says:

    Thank you for this tip, my external monitor has been useless ever since Mavericks and I reckon this has fixed it!! Tomorrow morning I’m also going to try it on my Mac mini which is connected to my TV via HDMI. That picture works just fine except when I’m playing movies via DVDPlayer. During that play back I get this really annoying horizontal shimmer line near the top of the screen that repeats every 10sec or so.

    • MickM says:

      This didn’t work for the Mac Mini problem. Oh well. At least it did work for the external monitor connected to my MacBook Pro.

    • Paul says:

      Follow up and let us know how it works for you, it has been a 100% success rate in our experience thus far with the issue appearing only after updating OS X!

      • MickM says:

        Well, I got about one day out of this fix for the external monitor connected to my MacBook Pro. I really thought everything was fixed, but just now my external monitor turned all snowy and I’m back to where I started.

        Playing movies using DVDPlayer on my Mac Mini connected to a TV via HDMI still has that really annoying shimmer. The fix never worked for that. One thing that we can all agree on is that all of this is Maverick’s fault.

  4. Bruce says:

    The official word:

    includes how-tos reset the SMC for desktops

    http://support.apple.com/kb/ht3964

    and our old friend the PRAM/NVRAM:

    http://support.apple.com/kb/ht1379

  5. Amigos says:

    Unfortunately, resetting SMC doesn’t help me. How do I know, that it had brought Mac to any effect? Coz the machine didn’t respond to touches – any signs for user, that it was reseted.

  6. Hlusta says:

    I’ve experienced this issue only twice so far. Reconnecting the HDMI cabel (out & in) worked just fine. Is this OK or not? Thx!

  7. Mack says:

    The SMC reset worked like a charm on my MB Pro (mid 2010) + LG Flatron E2211. Thanks!!

  8. marianne says:

    this did not work for mac mini, any other ideas? so annoying plus fatiguing on the eyes.

  9. Soup says:

    I had the “horizontal white line flickering issue” on the very top of the monitor associated with my MBP after associating temporarily said monitor with another computer.

    First startled, I tried associating the other computer again, but no issue with it, only with the MPB.
    Connecting/Reconnecting cables didn’t help.
    Restarting Computer/Monitor neither.

    Using the menu of the monitor itself to adjust the vertical position of the image manually or even using the image position auto-adjust solved my problem.

    By the way, I noticed that by changing the resolution of the external display the white line could move, sometimes appearing even on the bottom instead of the top of the screen.

    (MBP Mid 2009, running Mavericks)

  10. Allen says:

    This did not work for me. I have a MacBook Pro. OSX 10.8.5
    I did not make an OS update, this is the way the MacBook Pro came from the factory. The problem was there from the beginning.

  11. Chris says:

    I’m in same boat as Allen. SMC reset did not work. I have a circa 2014 MBP Retina 15″. I’m connecting to different 1920×1200 displays to it via HDMI. Both displays occasionally flicker off (black), and sometimes flicker into static snow mode for a few seconds. Very frustrating.

  12. Barry says:

    I have the same issue. Occasional black screen. HDMI to Samsung monitor. I have an early 2014 macbook air 13″. Resetting did not work for me either.

  13. Lars Olsson says:

    I have the same problem. MBP 13″ late 2013. Resetting SMC and PRAM temporarly solved my problem. Worked fine for a couple of weeks before it started again today.

    Resetting it now does not resolve the problem.

  14. Barry says:

    FIX: Update to OS X Yosemite if you can

    Today I installed OSX Yosemite on my Macbook Air 13″ early 2014 and my screen issues appear to be resolved.

    The OSX update fixed it. I’m relieved that it wasn’t a hardware issue. Apple should have fixed this software issue sooner.

  15. rhonda says:

    Didn’t work

    • IToin says:

      Great comment rhonda, no need to elaborate, just proclaim that you personally couldn’t figure something out. And so maybe your mac is flickering, maybe your mac is not, who knows? Good job Rhonda!

  16. Mauricio Marini says:

    I never had this issue before. Now, after Yosemite update 10.10.1 it started.

    I’m using a 17″ late 2011 i7 Macbook Pro and a LG W2353 external display.

    I tried both resets without success and after some research, I found in another post ( http://osxdaily.com/2014/11/17/os-x-yosemite-10-10-1-update-mac ) that other users are facing the same problem after this last update.

    Let’s wait for Apple’s call…. again!

  17. Mauricio Marini says:

    I just updated to 10.10.2 (BETA) and this issue persists.

  18. Mauricio Marini says:

    Second 10.10.2 BETA (Pre Release) doesn’t fix the problem.

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