iMac randomly shutting down and will not restart unless unplugged from mains

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Level 1

11 points

iMac randomly shutting down and will not restart unless unplugged from mains

I have a 2017 27" iMac (3.8GHz Intel Core i5) that randomly turns itself off.

The screen goes blank and the machine is dead. It will not restart unless I unplug it from the mains, leave it for 30seconds or longer and then plug it in again.

The problem started a couple of months ago and does not appear to follow any pattern. Sometimes it will run for several days without shutting down but sometimes it can happen 2 or 3 times an hour.

I have searched the web and there are numerous accounts of a similar problem but no one seems to have come up with a cause or remedy apart from replacing the internals.

Has anyone here had the same issue and managed to resolve it?

iMac 27″ 5K, macOS 11.1

Posted on Feb 1, 2021 12:13 PM

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Answer 1

Top-ranking reply

Jack-19

Level 8

46,002 points

Feb 7, 2021 1:13 PM in response to Jolly Boy A

Unfortunately, I would agree. Everything points to a hardware issue. Possibly a bad power supply.

I do not know what country/region you live in, but you can keep up to date on your Apple Store or AASP status here: Apple Store - Find a Store - Apple. (You may need to change your country on the site.)

I hope this helps.

Cheers,

Jack

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Answer 2

Jack-19

Level 8

46,002 points

Feb 1, 2021 8:33 PM in response to Jolly Boy A

Hi Jolly Boy A,

I believe we need to proceed with an EtreCheck report. EtreCheck is a useful app to diagnose issues, both hardware and software. It is trusted by many users. Please follow the steps outlined below:

Go to the Mac App Store and search for "EtreCheck."
Download it. It is a free and trusted app; as it is on the Mac App Store, and only trusted apps can be submitted.
Run the report, and put it in a post, as seen here - https://discussions.apple.com/docs/DOC-250000211

I think that you should also run Apple Diagnostics - Use Apple Diagnostics to test your Mac - Apple Support

Please post results of both!

Cheers,

Jack

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Answer 3

Jack-19

Level 8

46,002 points

Feb 2, 2021 3:33 AM in response to Jolly Boy A

The issues I see are Heavy Photos CPU usage and System Modifications, however, this would not cause the issue you are describing.

It seems that your issue may be a hardware issue. Did the Apple Diagnostic flag anything?

The next step is erasing the iMac and reinstalling macOS.

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Answer 4

Jolly Boy A Author

Level 1

11 points

Feb 2, 2021 4:17 AM in response to Jack-19

Thanks for looking, @Jack-19.

Apple Diagnostic stated no problems found.

However, after running Diagnostics the iMac couldn't be restarted in safe mode and I had to force a shutdown and then restart. I don't know if that is significant in any way.

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Answer 5

Jolly Boy A Author

Level 1

11 points

Feb 7, 2021 6:48 AM in response to Jolly Boy A

After a couple of calls with Apple Tech support, running all the diagnostic checks and disk utility I was advised to completely wipe my iMac and do a fresh install of the OS. Did that yesterday and for a few hours all seemed good. However, the fault has reappeared and my iMac has crashed 3 times today.

I haven't re-installed any files or programs so that discounts the problem being software related.

If it is a hardware issue, and all the evidence now points to that, I am stuffed as current lock down restrictions make a store visit impossible and I am left with an £1,800 desk top ornament!

Anyone got any advice or pointers that may help me, please?

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Answer 6

Jolly Boy A Author

Level 1

11 points

Feb 2, 2021 3:23 AM in response to Jack-19

Thanks, @Jack-19.

Here is the EtreCheck report:

EtreCheck Report for iMac random shut down problem

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iMac randomly shutting down and will not restart unless unplugged from mains

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