Jeremy Liu

Q: iMac (Retina 5K, 27-inch, Late 2015) Randomly Restarts Without Errors

My iMac has been randomly restarting itself (about once a day) when it is idle.  Has anyone else experienced the same problem?  I found a YouTube video and it is exactly what happened to my iMac:  https://www.youtube.com/watch?v=ka7lUIeiH5E

 

I witnessed it once -- the computer was on (not sleeping) with the display off, nothing CPU/GPU intensive running.  I suddenly heard a chime and saw that the computer restarted itself.  I logged in.  There was no pop-up window.  I launched Console and did not see anything unusual before the restart.

 

More information:

 

  1. The computer is idle when restart happens.  Nothing on the computer indicates it overheats.  Display is off (due to inactivity) and fan is quiet.
  2. There is no trace of software shutdown, kernel panic or crash.  System log shows normal activities and then a sudden BOOT_TIME entry, as if someone yanks the power cord.
  3. It is not a power failure because the computer should be off if it is really a power failure.  "Start up automatically after a power failure" is not checked.
  4. It started to happen after I came back from a trip and upgraded my iMac to the latest Mac OS X five days ago.  This computer was purchased last October and I had never seen something like this until a few days ago.

 

The comments on the YouTube video suggest a total replacement, but I'm reluctant to do so if it turns out to be a software/firmware problem that can be fixed. -- The computer is heavy and the nearest Apple Store is not very close, not to mention the backup/restore efforts.

 

Thanks

iMac with Retina 5K display, OS X El Capitan (10.11.4), Retina 5K, 27-inch, Late 2015

Posted on Apr 7, 2016 6:45 PM

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Q: iMac (Retina 5K, 27-inch, Late 2015) Randomly Restarts Without Errors

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