2011 iMac recently randomly restarts

Discussion in 'iMac' started by madeirabhoy, Mar 4, 2018.

  1. madeirabhoy macrumors 6502a

    Oct 26, 2012
    my iMac has been pretty trouble free for most of its life. i had the dodgy 6970m graphics card, but apple replaced that plus also the screen itself as it failed at the same time, that was maybe 18 months ago.

    now just in the last week ive noticed it randomly restarts. its sometimes when im using it, but also since i always leave it on, i know it does it when im not in as ive left apps open and they've been closed when i came in.

    it runs for hours of normal usage, and then suddenly ping, screen off, instant restart. only once have i really noticed it do it frequently. about 3 nights ago it did it 3 times in 30 minutes, but normally i sit all evening without it doing so but then the next day it will do it once.

    i worry its the power supply but theres not much plugged into it, one external usb drive, and i use it for charging my iPad. however ive just recently ordered a thunderbolt ssd which should arrive any day, guess a clean install on that will tell me if its software or hardware.

    any ideas?
  2. Lunder89 macrumors 6502


    Oct 16, 2014
    Did you install any new software recently? or updated a piece of software.

    What I am looking for is software that might cause this. I have had problems like this with some of Logitechs software for my Mac.
  3. AmazingRobie macrumors 6502


    Jun 10, 2009
    Hello. Since you're looking for ideas... RAM seated incorrectly can cause random reboots. I thought for a week or so that my laptop had s the bed, but started troubleshooting and realized it was the RAM. I have both crap computers produced by Apple with the faulty graphics chip from 2008 (Mbp) and 2011 (iMac). The 2011 iMac 27" has had the graphics card replaced twice, a faulty hard drive replaced twice and the display replaced once, but it's starting to cloud up on the right side again so I'll probably have to take it somewhere and have them see if they can get the dust out.

    Hopefully, the SSD fixes your issue, if not try swapping the RAM around and making sure it's seated securely.
  4. madeirabhoy thread starter macrumors 6502a

    Oct 26, 2012
    weird thing is, theres no error message, no 'your mac restarted because of a problem' it just starts up as if id told it to do it
  5. Hawaiian Starman macrumors member

    Oct 27, 2001
    Somerset West, South Africa
  6. T'hain Esh Kelch macrumors 601

    T'hain Esh Kelch

    Aug 5, 2001
    I've experienced random restarts in that model due to a faulty SATA cable, and a dying graphic card. And as people mention, dying memory can also give that symptom.

    If you can run from a secondary boot system, and it is stable, it is likely the SATA cable. As for RAM, try and run with only 1 of 2 sticks in the machine for a periode of time. And as for the graphic card, nothing you can do to troubleshoot it other than wait for the machine to stop booting eventually. So take your pick!
  7. madeirabhoy thread starter macrumors 6502a

    Oct 26, 2012
    10.13.4 beta (17E160e)
  8. nambuccaheadsau, Mar 4, 2018
    Last edited: Mar 4, 2018

    nambuccaheadsau macrumors 68000


    Oct 19, 2007
    Nambucca Heads Australia
    Suggest getting out of beta software. If the iMac has an SSD, full release of High Sierra. if a platter drive go back to Sierra or El Capitan.
  9. Hawaiian Starman macrumors member

    Oct 27, 2001
    Somerset West, South Africa
    Yes, totally agree about not using the Beta. Betas are not for day-to-day machines, that is unless you are inclined to surf the wave of confusion. ;)
  10. madeirabhoy thread starter macrumors 6502a

    Oct 26, 2012
    waiting on thunderbolt SSD arriving and will do a fresh high sierra install on it, but I'm wondering if its hardware because..

    1. theres a separate thread of a guy with the same symptoms and it was his graphics card
    2. I've had a few issues with usb power, once and only once I got a message about usb ports being turned off due to lack of power, but this could be the external drive as I'm in the process of slowly (usb2) copying everything off of it using my old mac mini as its been acting up. separately though the other day I plugged my iPhone in and it kept beeping as in charging, not charging, charging, not charging.
  11. Hawaiian Starman macrumors member

    Oct 27, 2001
    Somerset West, South Africa
    Did you uninstall the beta? If so, are the unexpected shutdowns still occurring?
  12. Fishrrman macrumors P6


    Feb 20, 2009
    For random, out-of-the-blue restarts, I'd suspect:
    - RAM
    - Power Supply
    - Failing GPU
    - Failing hard drive
    (not in any particular order)

    If the problem ends up being costly to repair, and the fact that the iMac is now approaching 7 years old, I'd start shopping for a replacement.
  13. madeirabhoy thread starter macrumors 6502a

    Oct 26, 2012
    not yet. as ive got a thunderbolt SSD arriving tomorrow i thought it easier to wait until it arrives and install fresh on that rather than trying to roll back on my internal HD
    --- Post Merged, Mar 8, 2018 ---

    was thinking that but tbh, this machine does everything i need it to, and is a 27", to buy a new 27" would cost me over €2000 so id end up paying north of €1000 downgrading from this to a new but smaller machine plus id have wasted money on the thunderbolt accessories.

    will depend on what it is i guess and how much it costs
  14. padams35, Mar 8, 2018
    Last edited: Mar 8, 2018

    padams35 macrumors regular

    Nov 10, 2016
    Is your mac configured to automatically restart in the event of a power failure? If yes then I'd bet the issue is power related: either a PSU issue or flaky line power.

    My 2011 started 'randomly' powering off at the slightest electrical flicker last year. Sudden black screen, no error message on restart. No clue if the cause was aging components on the iMac rendering it incapable of handling power fluctuations, degraded line quality, or a just a bad surge protector that was starting to "fail safe" but a new $20 EMI/RFI filtering surge protector fixed my random shutdown issue.
  15. madeirabhoy thread starter macrumors 6502a

    Oct 26, 2012
    good thinking, ive turned that off so i can find out.

    although its not restarted all day, always the way.
  16. madeirabhoy thread starter macrumors 6502a

    Oct 26, 2012

    okay so I now have a new thunderbolt SSD with a fresh install with minimal things added, automatic restart is turned off, I even changed it from the multiplug its plugged into along with the router/telephone/usb drive etc...and plugged it in to another socket which it only shared with my google home...

    and yesterday it restarted every 2 minutes for about say 10 restarts. would come on, id open safari, go to post something on another forum, one sentence in, I hear the hard drive stop, screen black, pause, bong, start up.

    one thing I noticed which could be coincidence, when it starts up (from the external SSD) the screen is bright, the bar loads to about halfway, it blanks for a second and then the screen is darker as the bar finishes.

    however after those 10 restarts, actually maybe it was about 5 or 6, it then worked all evening without a problem.

    I ran techtools, and it passed the ram and everything, the only thing that failed was the fan test, and that was specifically the internal HD fan, that drive though isn't being used for anything as I'm using the thunderbolt SSD for startup and a new 4tb usb drive through a thunderbolt to usb 3 adaptor.
  17. vkd macrumors 6502a


    Sep 10, 2012
    Theres a free app called Macs Fan Control, you could install it and monitor your fan & heat situation, see if it highlights anything.
  18. briloronmacrumo macrumors 6502


    Jan 25, 2008
    Just because the HD isn't used doesn't mean the fan isn't involved in the failure. iMacs need all the cooling they can get and a failing fan of any kind could contribute to higher temperatures. BTW: just because the GPU is only 18 months old doesn't mean it is still good. An appointment with an Apple Store to have them run full diagnostics ( usually no charge here in the USA ) would be my next step assuming keeping the 2011 iMac is the goal. Running Macs Fan Control ( or something similar ), as vkd noted, is also a good idea.
  19. madeirabhoy thread starter macrumors 6502a

    Oct 26, 2012
    maybe I shouldn't speak so soon...

    firstly I do wonder if my lucky white heather isn't having Civ VI open as it never seems to crash with that open. in fact screensaver won't even kick in when thats open..

    so thats one thing I've noticed...

    but the other, due to tech tools failing the internal HD fan, and since I have a new thunderbolt SSD running the machine and a new thunderbolt adaptor running a new 4tb drive, I figured id unmount the old HD.

    hasn't crashed in a week or more.
  20. madeirabhoy thread starter macrumors 6502a

    Oct 26, 2012
    can definitively say Civ VI stops it from restarting. just had to do an OS update, and it took me over an hour to get the machine to stay on long enough to get Civ VI open, as it still restarts right up until the game is properly open, so it would often restart as steam was opening or civ was or it was trying to open the save file.

    very frustrating and you don't think its ever going to work and about the 25th attempt after some near misses, I finally got the Civ VI save game opened and on screen. and now the iMac hasn't restarted in an hour.

    of course, this isnt the ideal solution, there must be something wrong, plus I can't always assume I will get Civ VI open in time....

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19 March 4, 2018