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iMac Turns Itself On

E

Eric Idle

macrumors 6502a
Original poster
Jan 4, 2020
639
517
What reasons might be that cause an iMac to come out of sleep mode by itself? Very often I find that my imac is on first thing in the morning after being put to sleep the day before. I cannot for the life of me figure out what is going on here. I have set no alarms or timers of any kind on this device. What should I look for to make this stop?

Thank you!
 
Disable "Allow Bluetooth devices to wake this computer" in Bluetooth system prefs under Advanced. Nothing else worked until I did this. Unfortunately, by doing this the only way to wake the computer from sleep is by pressing the power button on the iMac. But it will sleep!
 
Ugh I had this exact same issue this morning! I usually wake up between 7 and 8, but when I was rousing I noticed it was a bit bright. I tap my iPhone to wake it to see the time and it's 5:50am, and the brightness was the screen of my new iMac across the room. I grumbled out of bed to put it to sleep again.

At first I thought tapping the phone woke it up somehow but the iMac must have already been awake or else the brightness wouldn't have woken me up so early. I experienced this same issue on my 2017 iMac for awhile and I made some adjustments to settings such as what @AZREOSpecialist pointed out and it stopped finally last year. When I upgraded to the 2020 I set it up the same way, with one exception.

Do you also have an external hard drive that you use for Time Machine backups and your TM setting is set to Automatic? This was what completely corrected the problem for me in my case on the 2017. On the new 2020 when I set it up I thought maybe Apple fixed that weird waking up issue I was experiencing, so when I set up TM I used Automatic again. Seemed fine for a few days. Then a few days ago I get home from work and the iMac is on again after I put it to sleep when I left in the morning. Sleep is set for one hour so it must have happened just before I got in. And now this morning it woke me up when it woke up! So I disabled the Automatic setting and I'm hoping it completely stops.
 
PieTunes said:
Ugh I had this exact same issue this morning! I usually wake up between 7 and 8, but when I was rousing I noticed it was a bit bright. I tap my iPhone to wake it to see the time and it's 5:50am, and the brightness was the screen of my new iMac across the room. I grumbled out of bed to put it to sleep again.

At first I thought tapping the phone woke it up somehow but the iMac must have already been awake or else the brightness wouldn't have woken me up so early. I experienced this same issue on my 2017 iMac for awhile and I made some adjustments to settings such as what @AZREOSpecialist pointed out and it stopped finally last year. When I upgraded to the 2020 I set it up the same way, with one exception.

Do you also have an external hard drive that you use for Time Machine backups and your TM setting is set to Automatic? This was what completely corrected the problem for me in my case on the 2017. On the new 2020 when I set it up I thought maybe Apple fixed that weird waking up issue I was experiencing, so when I set up TM I used Automatic again. Seemed fine for a few days. Then a few days ago I get home from work and the iMac is on again after I put it to sleep when I left in the morning. Sleep is set for one hour so it must have happened just before I got in. And now this morning it woke me up when it woke up! So I disabled the Automatic setting and I'm hoping it completely stops.
Click to expand...

I do not have an external drive connected to my iMac all the time, so that's not the reason why it wakes from sleep. It has happened now 4 times today and I can't figure out why.
 
I prefer to have my computers turn off the monitors instead of sleeping. My CCC backup runs at 3am and sleeping could interfere with that.
 
Turning my bedside light on can trigger my iMac to wake up. It must create a small electrical spike. I turn off my iMac overnight to avoid that.
 
"What should I look for to make this stop?"

My suggestion works 100% of the time.

Get a power strip with an on/off switch.
Plug the iMac into it.

At night, shut down the iMac and switch OFF the power strip.
In the morning, switch the power strip ON and press the iMac's power-on button.

Do this, and it will never, EVER "wake up" at night.
100% guaranteed !
 
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You should run Activity Monitor and see if any programs are identified as preventing sleep on the Energy tab.
 
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