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  1. #1
    iMac Flickering Screen

    Member Since
    Jan 17, 2014
    Posts
    10
    iMac Flickering Screen
    I have a 21.5" iMac and the screen brightness flickers! It has posed zero problems on using the computer; everything works just fine and completely normal. The screen doesn't change colors nor does it go completely blank or anything like that. It's almost as if some auto-brightness display feature is freaking out and constantly trying to adjust. It adjusts the brightness completely on its own and completely random. Any thoughts?

    It doesn't seem to be creating any types of problems with the display; just really annoying!

  2. #2
    iMac Flickering Screen
    harryb2448's Avatar
    Member Since
    Nov 28, 2007
    Location
    Nambucca Heads Australia
    Posts
    20,000
    Specs:
    iMac i5 2.7GHz, 16GB memory, OS 10.10.5
    Any chance the iMac is still under AppleCare warranty?

    Sounds like it MAY be a backlight problem. You would need to get it diagnosed and perhaps if not under warranty have a go at it yourself, depending on the precise model:-

    Intel iMac 21.5" LED Backlight Board
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

  3. #3
    iMac Flickering Screen
    MYmacROX's Avatar
    Member Since
    Mar 17, 2009
    Posts
    3,626
    Specs:
    2008 15" MBP Yosemite, 2012 21.5" iMac Yosemite
    I assume you've already looked at the auto-brightness settings and turned that feature off.

    Do you have Apple Care for your iMac, or is it still under the 12 month warranty period?
    64GB iPhone 6, 64GB iPad Air 2.

    Reminder: Please include your Mac's specs. This will make it much easier for the other members to assist you.

  4. #4
    iMac Flickering Screen

    Member Since
    Jan 17, 2014
    Posts
    10
    No warranty...she's a few years old. May have to live with it.

    I'll try turning off the auto adjust...where's that at? Found the brightness, but not the auto??

  5. #5
    iMac Flickering Screen
    harryb2448's Avatar
    Member Since
    Nov 28, 2007
    Location
    Nambucca Heads Australia
    Posts
    20,000
    Specs:
    iMac i5 2.7GHz, 16GB memory, OS 10.10.5
    Depending on your operating system found in System Preferences > Displays > Display and a selected box under Brightness. Good luck.
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

  6. #6
    iMac Flickering Screen
    chscag's Avatar
    Member Since
    Jan 23, 2008
    Location
    Fort Worth, Texas
    Posts
    45,170
    Specs:
    27" iMac i5, 3.2 GHz, iPad 3, iPhone 5c, iPhone 6+, 3 iPods, Yosemite
    In addition to the advice received from Harry, also try resetting the System Management Controller. You do that by shutting down your iMac, unplugging it from the AC socket, let it set for about 15 minutes, plug it back in and reboot.

  7. #7
    iMac Flickering Screen

    Member Since
    Jan 17, 2014
    Posts
    10
    Quote Originally Posted by harryb2448 View Post
    Depending on your operating system found in System Preferences > Displays > Display and a selected box under Brightness. Good luck.
    I don't have a box under the brightness slide bar...interesting!

  8. #8
    iMac Flickering Screen
    harryb2448's Avatar
    Member Since
    Nov 28, 2007
    Location
    Nambucca Heads Australia
    Posts
    20,000
    Specs:
    iMac i5 2.7GHz, 16GB memory, OS 10.10.5
    Hard to suggest further you have not supplied operating system details alas.

    System Preferences do differ between OS X.6, X.7, X.8 and X.9.
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

  9. #9
    iMac Flickering Screen

    Member Since
    Jan 17, 2014
    Posts
    10
    OS X 10.9.1. with Mavericks installed. Problem was occurring before Mavericks though.

  10. #10
    iMac Flickering Screen
    harryb2448's Avatar
    Member Since
    Nov 28, 2007
    Location
    Nambucca Heads Australia
    Posts
    20,000
    Specs:
    iMac i5 2.7GHz, 16GB memory, OS 10.10.5
    Well rather than a box maybe I should have said a tickable radio button. Make sure it is not selected.
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

  11. #11
    iMac Flickering Screen

    Member Since
    Jan 17, 2014
    Posts
    10
    No box underneath the brightness slide bar!

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