iMac 21.5" 2019 turns on by itself!

Question

Level 1

11 points

iMac 21.5" 2019 turns on by itself!

Hi everyone,

for a few days my iMac (Retina 4K, 21.5 inches, 2019, Big Sur 11.7.10) every time I turn on the power strip to which it is connected turns on itself, without pressing the start button.

I specify that the energy saving settings are those of default and that the settings from saving energy "active for access to the network" and "automatically starts after current interruption" are deactivated.

What can be due to? Advice?

Thanks

iMac 21.5″, macOS 11.7

Posted on Sep 27, 2023 12:04 AM

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Answer 1

Top-ranking reply

den.thed

Level 10

88,714 points

Oct 4, 2023 05:40 AM in response to John436

Switching the power strip on and off can foul up the System Management Controller.

Try resetting the SMC, as per > Reset the SMC of your Mac - Apple Support

Desktop computer

Shut down your Mac, unplug the iMac's power cord.
Wait 15 seconds, then plug the power cord back in.
Wait 5 seconds, then press the power button to turn on your Mac.

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Answer 2

WheelieNick

Level 8

45,425 points

Sep 27, 2023 02:10 AM in response to John436

Try and boot the Mac in the safe mode to see if the issues persist

Turn on or restart your Mac, then immediately press and hold the Shift key until you see the login window.
Log in to your Mac.
You might be asked to log in again.
On either the first or second login window, you should see “Safe Boot” in the menu bar.

If it does not persist In the safe mode, the problem is caused by an external piece of software, you might want to evaluate the software installed to your Mac

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Answer 3

WheelieNick

Level 8

45,425 points

Sep 28, 2023 05:12 AM in response to John436

You might want to review these settings. When using macOS 11 like stated in your above message, see this Link for instructions

If your Mac won’t go to or stay in sleep – Apple Support (UK)

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Answer 4

John436 Author

Level 1

11 points

Oct 9, 2023 12:16 AM in response to den.thed

Ok.

I tried with another power strip and another power outlet but the problem remains.

I reset smc, turn off and turn on power strip and the Mac doesn't turn on itself. At the second attempt instead turns on by itself.

I attach activity monitoring and preferences saving energy. Have the preferences corrupted?

Can you understand what it is due to?

Is it an hardware problem?

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Answer 5

John436 Author

Level 1

11 points

Oct 4, 2023 01:12 AM in response to WheelieNick

I checked all the settings. Energy Saver I have deactivated everything, there are no scheduled switches on.

BT is turned off and there is no sharing.

I thought it was Microsoft Update, I installed all the updates but the problem remains.

I turn off the Mac, make sure it's turned off and unplug the power strip. When I turn the power strip back on the Mac turns on by itself!

Any other advice?

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Answer 6

ku4hx

Level 7

23,640 points

Oct 6, 2023 02:37 AM in response to John436

"I don't know what else to do."

----

Leave it on.

We have four Macs that run 24/7. Macs are made to operate ... let it. 2015 to 2020 models have never had a problem with 24/7 operation. Neither has they one MBP we use sporadically for that matter.

If you're ultra energy conscious, put your power strip where you can get to it easily and kill the power once the Mac is off.

Maybe pull the plug once the Mac does its short shut down thing. There are are always solutions, you just have to commit to using them.

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Answer 7

den.thed

Level 10

88,714 points

Oct 6, 2023 06:09 AM in response to John436

John436 wrote:

I did the SMC reset. It resolved for once and then started again.

I'll try changing the power strip. I don't know what else to do.

Seems like turning off the power strip is fouling up the iMac's System Management Controller.

Reset the SMC again, then only shutdown the iMac and leave the power strip on.

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Answer 8

John436 Author

Level 1

11 points

Sep 28, 2023 04:59 AM in response to WheelieNick

I started the Mac in safe mode, then turned off the power. I turned the power back on and it turned on again by itself!

Any other advice?

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Answer 9

ku4hx

Level 7

23,640 points

Sep 28, 2023 07:15 AM in response to John436

How are you tuning the Mac off?

If you have it set to restart after a power failure and you're shutting it down with the strip power button, it'll restart thinking power has been restored.

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