1. SprSynJn's Avatar
    When Power Nap is activated on my iMac, often a failure will occur when it tries to wake up from standby which will then result in a force restart, often in the middle of the night. Is the Power Nap function reserved only for SSD drives? My iMac does not have one. Or is my HDD not working as intended?

    Should have posted this in the iMac forums actually, anyway it can be moved?
    10-07-2017 08:42 PM
  2. SprSynJn's Avatar
    Just me then aye? Darn...
    10-12-2017 08:21 AM
  3. Raptor007's Avatar
    Not just you, I often find my late 2016 MBP did a restart when I go back to use it later for no reason. I suspect High Sierra is the issue, but I am stuck on that OS now since you can't go back to Sierra. I didn't make a backup as I normally do.
    12-26-2017 10:14 AM
  4. doogald's Avatar
    Not just you, I often find my late 2016 MBP did a restart when I go back to use it later for no reason. I suspect High Sierra is the issue, but I am stuck on that OS now since you can't go back to Sierra. I didn't make a backup as I normally do.
    Unless it is an iMac Pro, I believe that you can still download Sierra. See https://support.apple.com/en-us/HT208202

    And I believe it's possible that one of the options when you boot from your Recovery partition is to install the original OS that the device shipped with. See https://support.apple.com/en-us/HT204904 (I just saw this page last week when I reinstalled High Sierra from scratch last week myself without migrating because I was having some weird issues and I suspected it was from some old app cruft.)
    12-26-2017 04:00 PM
  5. SprSynJn's Avatar
    This has been happening to my machine a lot longer than High Sierra has been out. I would wager to say that it has happened since I got the device, which was back in 2013. Turning off Power Nap seems to resolve the issue, although the other day I swore it restarted by itself once again, even without the feature activated. I wonder if macOS automatically restarts the device when a security patch is downloaded in the background. It seemed to restart twice in one go.
    12-26-2017 06:39 PM
  6. dmoskaluk's Avatar
    Since the update/upgrade from Sierra to High Sierra, my 2012 iMac has been having totally random reboots while sleeping, then showing a warning about the reboot because of a problem, with a long diagnostic wrt 'sleep wake failure'. The normal sequence seems to also involve 2 reboots back to back. The computer is fine once in use, albeit wake-up now takes a while and seems to be very slow to get Bluetooth ( control of mouse & keyboard) back from sleep..... This has happened since the High Sierra install and the latest security etc update ( 10.13.2) didn't fix.... I'm waiting for the next bug fix update (10.13.3) due soon before digging further though....
    01-07-2018 04:58 PM
  7. dmoskaluk's Avatar
    01-08-2018 07:17 AM
  8. dmoskaluk's Avatar
    Can't attach the screen warning but it comes on 2 or 3 times a day after the sleep/wake restarts...
    01-08-2018 07:19 AM
  9. SprSynJn's Avatar
    Do you have Power Nap enabled?
    01-08-2018 07:25 AM
  10. dmoskaluk's Avatar
    I did but disabled it quite a while ago ( a month??) thinking it may have had something to do with this problem - it didn't.....
    01-08-2018 04:06 PM

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