IMac Shut Down Random

Hello prodreso,

Thank you for using Apple Support Communities!

I understand from your post that your iMac is randomly shutting down. The following article has steps which may help resolve this type of issue:

If your Mac spontaneously restarts or displays a message that it restarted or shut down because of a problem - Apple Support

Best Regards.

That's a sign of a bad power supply. Had the same symptoms on an 2014 27" iMac. It took me 3 visits to the Genius Bar and several phone sessions with Apple engineers before Apple would replace the power supply (it was still under warranty). They wanted to rule out any software so had me finally erase the drive and install a new, clean system without any of my files. That confirmed that it was hardware related.

Since your iMac is a vintage model you'll have to take it to an Apple service provider for service.

Great. It seems in most cases this is the cause. I’m well out of warranty so I expect I can ask Apple to do anything as I’m paying for it. Mine is a late 2015 model.

im very Mac savvy, ruling out some other things to be sure then I’ll go with the power change.

after 3 days of powering off my Mac each night from 2300 - 0800 I haven’t had any issues. That’s only with minimal use in the evening though.

I would recommend against replacing the power supply yourself. An error can be fatal to both you and the computer, obviously you are more important. Please for the sake of safety let an AASP do the work for you.

Did the power supply change fix your problem?

Are you able to restart your iMac by just pressing its power button?

Yes. Haven't had a problem with it since.

Thanks for coming back to me..!

Yeah don’t worry I’ll ask Apple to do it for me. Just hope it’s the right fix as there are multiple forums on this issue saying this doesn’t always fix it.

Since it’s a vintage machine Apple won’t work on it. You’ll have to find an Authorized Apple Service Provider.