I have recently faced a critical issue with my iMac (since June 2016). The problem showed up after installing OSX El Capitan. It shutdown randomly and suddenly. It's as if the power cord has been disconnected. And it doesn't restart when I press the power on button. I have to switch off the power socket, wait for a few minutes, then it can be turned back on.

After 3 visits to Apple Store to fix this, they ran same test to see if it's a hardware- or softwareproblem (negative), the ram-module is replaced, they have done a clean install and it's still the same problem.

Is there anyone who has a solution for this problem?

to be continued...

  • 1
    If the Apple store can't resolve the issue after 3 visits then you should tell them to do a warranty replacement on the iMac.
    – fsb
    Oct 4, 2016 at 13:40
  • my Mac is no langer under warranty... Oct 5, 2016 at 11:26
  • Apple have been known to do repairs/replacements for hardware outside of the warranty period. Of course, each case is different. In any case, can you edit your question to provide details of your iMac? Please include your particular model, RAM, SSD/HDD, CPU etc. Also, what exact version of El Capitan are you running? And, what version of MacOS were you running prior to installing El Capitan?
    – Monomeeth
    Oct 5, 2016 at 12:29
  • The first thing you need to do is find out what the "shutdown cause" is. You can find it in the syslog. Issue this command: syslog | grep shutdown and post your results.
    – Allan
    Nov 3, 2016 at 16:39

1 Answer 1


I can't imagine the Apple Store haven't already done this - but have you/they tried resetting the SMC?

For iMacs, the steps to do this are:

  1. Shut down your computer
  2. Unplug it from the power socket
  3. Press and hold the power button for 5 seconds
  4. Plug it back in and turn it on.

However, assuming they have already tried this, there are other things they can do, such as swapping over the logic board.

Troubleshooting is a process of elimination, and you know that reinstalling macOS doesn't resolve the issue, and neither does replacing the RAM. So, if it was me, the logic board would be next.

Let us know how you go.

  • 1
    apparantly there are other mac-users who have the same problem. The logic board is, according to them not the problem, they've replaced it and the problem stays the same... Oct 5, 2016 at 11:28

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