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late 2009 21" iMac screen flickering

3237 Views 8 Replies Latest reply: Jan 5, 2014 1:01 PM by Mr Morrison RSS
macfromrome Calculating status...
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May 7, 2013 8:58 AM

My late 2009 21" iMac recently developed a screen flickering issue. The screen does not flicker constantly, just now and then, but it flickers several times every day. When it flickers, the light level sometimes decreases for a while. This flickering has occurred within the first few minutes of use as well as after many hours of use. I have installed all updates as they are released. I know the 27" iMacs of the same era had this flickering problem and that Apple issued a firmware update for those iMacs. I can't find any information about this issue in 21" iMacs.  Does anyone else with a 21" iMac have this problem? Does anyone have a fix?

iMac, Mac OS X (10.6.8), late 2009 1TB replacement HD
  • seventy one Level 6 Level 6 (8,445 points)
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    May 7, 2013 9:29 AM (in response to macfromrome)

    Hi macfromrome,


    Run through the contents of 'More like this' to the immediate right of your initial post.   There are several people with this problem and one or two, especially in the link post below,  Kaos2K, from Spain, who has what seems a realistic explanation


    [GUIDE] Fix iMac flickering and dark...: Apple Support Communities

  • seventy one Level 6 Level 6 (8,445 points)
    Currently Being Moderated
    May 7, 2013 10:51 AM (in response to macfromrome)

    I was really looking for clues rather than anything else.   I am not sufficiently tech savvy for more in this case.    But don't forget the links within the 'More like this' posts.   If you have the time you can drift through an amazing amount of detail.   Good luck.

  • Harleygold Calculating status...
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    Jul 7, 2013 6:59 AM (in response to macfromrome)

    I have the same set up as the original post and in the last few days, my screen has been noticably flickering dim to bright.  Not a drastic dim but still very noticable.  Has this topic been resolved yet?

  • surferic123 Calculating status...
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    Aug 25, 2013 9:11 AM (in response to macfromrome)

    Hi i experienced the exact same issues with my 21" iMac from late 2009 a few months ago.. Started with flickering and the brightness went down.. i didn't care too much then. But a few week ago it became really annoying!


    And a few days ago my screen went all black! The computer works fine because i have a second monitor that i now use as a primary! And everything runs good.. But the iMac screen is now black all the time..


    when i start up the computer it can come on for a few seconds but immediately goes back to black!


    Have you experienced any of this? Or did it just stop? what should i do?

  • pgowdie Calculating status...
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    Aug 27, 2013 8:14 PM (in response to surferic123)

    very similar issues with sporadic screen dimming and brightening with my 27" iMac Mid 2011. running 10.7.5; processor: 2.7 GHz Intel Core i5; 20GB memory.


    no apparent rhyme or reason. flickers now and then. started about a month ago. i've read macfromrome's latest tread regarding testing with an additional external monitor and would like to find another way to troubleshoot as again, no rhyme or reason when it does it and this machine is my work horse.


    macfromrome's theory about heat and using an air conditioner may have some validity. i work in a basement with a steady temperature of 19 degrees celsius. i sometimes reach behind the iMac for stuff and it often feels very warm. so wondering if it's a overheating issue.

  • Mr Morrison Calculating status...
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    Jan 5, 2014 1:01 PM (in response to surferic123)

    surferic123, this is exactly the problem that I'm trying to resolve. Please let me know if you find a solution.


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