iMac (2017 27") shutting down unexpectedly

[Atalla]

Hello folks - I'm a new iMac owner (existing MacBook user) and I'm having some trouble with my iMac with regard to screen saver, sleep and shutdown. Posting here as I assume it is a software problem, but who knows. As far as I can tell, I've got my Mac setup to not sleep when the screen is off and never turn off the screen, but after some amount of time (not sure how much as it is typically when I leave my office), the iMac shuts down. Totally shuts down, not sleeps. Maybe I leave the office for a long meeting or leave for the day and come back in the morning and I have to power up the Mac, I get the black screen apple logo and progress bar. I log in and all my apps have exited.

Pasted my Energy Saver settings below and I have no schedule setup for automatically booting/waking or sleeping/shutting down.



I have a hot corner setup for the screen saver. What I'd ideally like to happen is for the Mac to never sleep or shut down unless I proactively tell it to sleep or shut down. When I leave my desk, I want to drop the cursor to the hot corner for screen saver (which requires password immediately) and otherwise have nothing happen. I'm at a loss as to why it keeps shutting down. Any tips from more experienced MacOS and iMac users?

Thanks in advance.

 

[MacInWin]

Could be Power Nap. Here's Apples documentation on it: https://support.apple.com/en-us/HT204032

 

[Raz0rEdge]

A couple of questions. What is your reason to not let the computer go to sleep if you are going to be away and using a screen saver anyway? What applications are normally running? Before heading home, close all the applications and leave just the OS running and see if it survives the night.

 

[Atalla]

Could be Power Nap. Here's Apples documentation on it: https://support.apple.com/en-us/HT204032

Thanks. I read through that. I read that this setting is only relevant when the computer is already asleep. I'm trying to prevent sleep. Also, I notice that the screen capture for desktop Energy Saver settings is different in that article than I see. I don't have the independent sliders for screen sleeping and computer sleeping. This led me to note that I'm not running High Sierra yet. I'm not sure why I didn't check this but I just assumed that the Mac would automatically update to the newest OS out of the box. I'm going to do the High Sierra update and then see if any behavior changes occur.

 

[ferrarr]

Personally, I would uncheck both “Put Hard Disks To Sleep When Possible”, and “Enable Power Nap”. Test these settings and go from there.

 

[Atalla]

A couple of questions. What is your reason to not let the computer go to sleep if you are going to be away and using a screen saver anyway? What applications are normally running? Before heading home, close all the applications and leave just the OS running and see if it survives the night.

Yes. Will do this. I had originally expected this to be the default behavior just based on my Macbook experience. It was the fact that the computer was shutting down on its own that troubled me. If I can get it to stop shutting down, I'll be glad to let it sleep. I should add that I manually put the computer to sleep one day and it still had shut down fully overnight. Totally confused me. Have the hard drive sleep and Power Nap disabled for now to see what happens.

 

[chscag]

@Atalla:

You might want to consider using a power leveling UPS in your office and keep the iMac on it at all times. There may be other reasons your iMac is shutting down at night - like power glitches and or interruptions. Have you thought about that?

 

[Atalla]

Yes, although I'm not seeing any app level errors on reboot. Chrome doesn't pop the "shutdown unexpectedly" error and Office apps don't have potential data loss warnings. It shows every sign of a clean shutdown.

 

[chscag]

OK... here's something else you can try:

Go to System Preferences, Security & Privacy, click on the small lock at the bottom and enter your Admin password. After the lock opens, click on the "Advanced" box. Now, check the setting "Log out after" to see if you have anything there.

Sometimes, that will cause a shut down if that option has been selected for a certain time.

 

[Atalla]

OK... here's something else you can try:

Go to System Preferences, Security & Privacy, click on the small lock at the bottom and enter your Admin password. After the lock opens, click on the "Advanced" box. Now, check the setting "Log out after" to see if you have anything there.

Sometimes, that will cause a shut down if that option has been selected for a certain time.

Thanks. Good flag, but nothing there is set.

 

[chscag]

Thanks. Good flag, but nothing there is set.

The only thing I can think of then is that your iMac is shutting down because of a power fluctuation or it has a problem with its power supply. You might want to keep a close eye on it and before your warranty expires, have Apple look at it.