Strange iMac issue

[GW208]

I have a curious issue with my computer waking up and was wondering if anyone has any ideas of what might be causing it.
Every Sunday morning, and only Sunday morning, and only between the hours of midnight and 8AM the computer will randomly wake up several times on its own.
I've looked at some of the suggestions on the Apple forums but they don't seem to apply to my case. This is the only Apple product in the house and I've tried turning off my android phone to make sure it wasn't causing it. I could turn the computer off but I don't want to do that in case its Apple doing something.
Any suggestions or thoughts would be appreciated.

[Cheez-It Guy]

Is this one of the posts you've already reviewed?:

https://discussions.apple.com/thread/8439111

[GW208]

Is this one of the posts you've already reviewed?:

https://discussions.apple.com/thread/8439111

Yes it is and I think I have it set up properly. I have everything unchecked in energy saver and I have do not disturb set for 10PM-7AM in notifications.
The mouse and keyboard are wireless but I don't think that could be the problem.

[Bogle7]

" I deactivated the Bluetooth wake on Bluetooth access and my computer slept all night for the first time in two weeks"

[Target2019]

My first guess is that the computer is looking to do a scheduled time machine backup, and the backup media is not present.

[GW208]

" I deactivated the Bluetooth wake on Bluetooth access and my computer slept all night for the first time in two weeks"

I will try this next week but as far as I know the only Bluetooth devices are the mouse and keyboard. I would think if one of these were acting up the issue would be more random?

My first guess is that the computer is looking to do a scheduled time machine backup, and the backup media is not present.

This sounds like a very good guess as I don't have a backup connected. When I look in time machine though, automatic backups are turned off.

[inverter]

Under Activity Monitor > Energy, do you have any unexpected apps preventing sleep?

[abyan]

If it’s only happening once a week, that doesn’t sound like Time Machine, which should be backing up every hour. It almost sounds like a routine weekly maintenance. In facts, I just checked my iMac, and there are in fact weekly maintenance scripts that run. They seem to run them overnight, often on Sundays, but not always. I can’t help beyond this, but happening once a week sure sounds like a routine that’s running. Have you tried apple’s phone help? I haven’t tried them during the plague, but otherwise have found they can be very helpful.

[Target2019]

" I deactivated the Bluetooth wake on Bluetooth access and my computer slept all night for the first time in two weeks"

I will try this next week but as far as I know the only Bluetooth devices are the mouse and keyboard. I would think if one of these were acting up the issue would be more random?

My first guess is that the computer is looking to do a scheduled time machine backup, and the backup media is not present.

This sounds like a very good guess as I don't have a backup connected. When I look in time machine though, automatic backups are turned off.

My second guess is System or App checking for updates, etc.

[rustymutt]

That's default timing for many security utilities that might be waking the computer. Backups, updates, and scans. Try locking the computer when signing out on Saturday. Also check your network adapter for "network wake" enabled/disabled. You'll figure it out.

[abuss368]

It may be your energy saver settings. Have you considered calling Apple support or peached their support forums? I have found that very helpful.

https://support.apple.com

[GW208]

That's default timing for many security utilities that might be waking the computer. Backups, updates, and scans. Try locking the computer when signing out on Saturday. Also check your network adapter for "network wake" enabled/disabled. You'll figure it out.

I don't know what you mean by network adapter?

Also, I've looked at the energy saver settings in 2 different places and I don't see anything that would cause this.

I took the advice to go to Apple support this morning and got a call from them within a few seconds. The lady I talked to was quite sure it wasn't Apple doing anything that would make the computer wake up. Her first suggestion was also to disable Bluetooth and if that doesn't work I should try resetting the SMC by turning the computer off and unplugging it for 15 seconds.

Thanks everyone for your suggestions, they have given me several things to check.

[Dottie57]

My first guess is that the computer is looking to do a scheduled time machine backup, and the backup media is not present.

+1. This happened to me. It took a lot of searching todigure out.

[fljones3]

Don’t know what it is but you could take a look at the logs. My guess is the macOS is doing its daily, weekly, and monthly maintenance routines. I have not looked to see when they are run. What do your logs look like?

[boomer_techie]

Every Sunday morning, and only Sunday morning, and only between the hours of midnight and 8AM the computer will randomly wake up several times on its own.

I don't have a solution, just a hint as to what the problem may be:

Several OS versions ago, Apple changed the functioning of system sleep. The system now "wakes up", does some housekeeping, and goes back to sleep. The screen is supposed to stay off during this.

There was some problem that seemed to affect the 12" MacBook. The computer would wake up and not go back to sleep. People would go to use their computer and the battery would be totally discharged. I think others would open their laptop bag to find a roasting hot computer that had shut down due to overheating. A common theme was iCloud - the system was trying to connect but couldn't.

I think Apple made some system changes that eventually fixed the problem. Or they may have caused it to misbehave in a different way.

Part of the problem is due to a system variable set to the wrong value. The operation of this variable is poorly documented. It also works differently on different systems. Quite possibly doing an OS upgrade may leave the variable set to the wrong value. (Sorry, I don't remember the variable name.)

...

A suggestion: Back up all your data. Twice. Now do a totally clean OS reinstall. I think it works to use the Installer on the Recovery partition. See: https://support.apple.com/en-us/HT201314 I'd start by erasing the disk (actually just the main partition) with Disk Utility. Then reinstall your programs and reload you data.

I realize that this solution is like getting rid of an ant infestation with a nuclear bomb!

[GW208]

Don’t know what it is but you could take a look at the logs. My guess is the macOS is doing its daily, weekly, and monthly maintenance routines. I have not looked to see when they are run. What do your logs look like?

I'm not computer savvy at all so had to search the internet for where to find the logs. I found them but they are just gibberish to me and I have no idea of what to look for.

Every Sunday morning, and only Sunday morning, and only between the hours of midnight and 8AM the computer will randomly wake up several times on its own.

A suggestion: Back up all your data. Twice. Now do a totally clean OS reinstall. I think it works to use the Installer on the Recovery partition. See: https://support.apple.com/en-us/HT201314 I'd start by erasing the disk (actually just the main partition) with Disk Utility. Then reinstall your programs and reload you data.

I realize that this solution is like getting rid of an ant infestation with a nuclear bomb!

Thanks but that is way beyond my comfort level or ability.

I think the best and easiest thing for now is to try turning off Bluetooth Saturday night and start from there.

[abuss368]

My first guess is that the computer is looking to do a scheduled time machine backup, and the backup media is not present.

+1. This happened to me. It took a lot of searching todigure out.

This is interesting. I presently have our backup hooked into an Apple wireless router - Airport Extreme. The backup is wireless (i.e.no cable involved).

[Ice-9]

My iMac was waking unexpectedly, and I pinpointed it to my leaving quite a large number of browser tabs open frequently. I realized if I closed Chrome, the iMac would sleep as expected. Your mileage may vary.