iMac Shutting Down Randomly

Discussion in 'iMac' started by PsYkOoOoO, Aug 18, 2014.

  1. PsYkOoOoO macrumors newbie

    Aug 18, 2014
    Hello MacRumors!

    I am posting here for the first time because I am handling a rather tricky case here.

    My girlfriend's iMac (21.5-inch, Late 2012, running Maverick) has been displaying some issues as of late. Particularly, it'd refuse to turn on from time to time. Also, if she puts it to sleep at the end of the day, the iMac will be switched off by morning and will refuse to turn on. Pressing the power button, the keyboard and the mouse does nothing to power the iMac up.

    The strange thing, however, is that if she lets the problem sit for a day, for example, the iMac will come back to life for a few hours to a few days before the same thing happens again.

    I have tried a couple of things, and I will list them down:

    1. SMC and PRAM resets
    2. Apple Hardware Test (No problem detected whatsoever)
    3. All the checks in Disk Utility and Onyx.
    4. Removed all third-party hardware to isolate the problem. It's still happening.

    Now, at this point, I figured it is probably a hardware problem not previously detected by the Apple Hardware Test. I figured it is probably the Power Supply Unit being faulty, or perhaps the cable. However, I noticed something strange just yesterday. The iMac is able to run the entire day if I force it to run processes that require the computer to be turned on. For example, backing up via Time Machine, as well as downloading movies. These processes seem to keep the iMac turned on without random shutdowns. I have a feeling that, because of this, it is not a hardware issue that's related to power supply at all.

    The one thing that I have yet to try yet is reinstalling Maverick via a bootable drive or Maverick's in-built reinstallation feature. Do you guys think that a clean reinstall (with a Time Machine backup of course) may potentially solve the problem?

    Thank you so much!
  2. macthefork macrumors 6502

    Feb 2, 2013
    Are you sure the iMac isn't plugged into a switched outlet? I came across that problem once where the computer only seemed to work at certain times of the day. I found that it was plugged into an outlet that was controlled by a switch on the wall. Is there power to the plug when this is occuring?

    If it's not that, it does sound like some kind of intermittent hardware problem, possibly in the Power Supply.
  3. PsYkOoOoO thread starter macrumors newbie

    Aug 18, 2014
    I am coming at you from a country where wall outlets do not usually come with switches. I have also swapped wall sockets and the problem persisted. I should also add to the original post that I have yet to change the power cable.
  4. Rud3Bwoy Suspended


    Oct 9, 2011
    ill say this much those apple test etc sometimes aren't reliable apple test/memtest/remember all told me my faulty ram had no issues mind you it did and i had to do a rma.

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