iMac Shutting Down Randomly – Seeking Advice

[seymeng]

Hello Everyone,

In mid-2011, I purchased a 27-inch iMac. Recently, I started using OpenCore Patch to install macOS Sequoia 15.0.1, which worked perfectly for a couple of days. After that, I updated to version 15.0.2 using OpenCore Patch again. During this time, I also installed and tested the Setapp application. Although I’m not sure if it’s related, a few hours after installing Setapp, my iMac began shutting down unexpectedly.

When the iMac shuts down, it attempts to restart, but the screen remains blank. To troubleshoot, I reverted to macOS High Sierra, but the issue persists: the iMac shuts down within 2–3 minutes of operation. After shutting down, I have to wait at least 20–25 minutes before it can power back on.

I carefully opened the iMac and checked all connections. The fans appear to be working correctly. Currently, I suspect the power supply might be the problem, as the system seems to require cooling time before restarting.

I would greatly appreciate any advice or suggestions to help me resolve this issue.

Thank you all in advance!

 

[HobeSoundDarryl]

Best guess: age has caught up with that iMac at 14 years old. There are abundant threads here and elsewhere about power supplies and logic boards finally conking. I had the same kind of problem myself with a 2010 one back in about 2019 or so.

The good news is that a local shop can replace the power supply for relatively little money if you don't have those skills yourself. However, that money may be best spent towards buying a new Mac for a fresh 14 or 10 or whatever term these Silicon Macs will be allowed to last (much more locked down than that iMac). You might spend the money to fix the power supply and then the logic board conks... or the screen finally quits... or this or that.

Apple seems to favor about a 7 year lifespan, after which about all Macs are soon "vintaged." You've got 2X Apple's apparent target. Perhaps harvest what you can- keyboard, mouse, internal storage- and get yourself a new one with a "fresh start" on the 7-year replacement cycle clock?

If you want to play the cause & effect hypothesis all the way out before faulting the hardware, pull the internal drive, clone it (for potentially switching it back later) and then install base macOS on it (with no third party hacks). Reinstall it and fire up the iMac. With no "third party" what if in play, you'll either confirm or refute the software-driven hypothesis. If it boots, perhaps slowly reinstall or migrate your stuff from the clone to get it back to a functional Mac again.

You should also try booting into "safe mode" to screen out the third party software for a more pure boot.

But my guess is that the software update is only coincidental and that you have a hardware issue: power supply, logic board, maybe internal drive, maybe something else. 14 years is a LONG ride on Mac hardware... much longer than most. Apple quit your Mac many years ago. The most practical move may be for you to quit on it too.

 

[Fishrrman]

Sumthin' tells me that the fact that you're using the open core patch has a lot to do with it.

Also... now going on 14 years old... age is a factor, as well.

 

[basdeninard]

Nobody here can tell you what the problem is, but it could be the power supply. As it happens, the power supply unit on my 2017 iMac died just last week. My local Apple Authorised Service Provider replaced the faulty power supply and it's working fine again.

I find it strange that users in the Mac world are quick to jump to the conclusion that the logic board might be the problem. Let's reverse this, and talk about a PC. How often do you hear of a motherboard just suddenly dying on a PC? That's right. Not very often.

Given the age of your machine, you need to weigh your options. Is it really worth getting your iMac fixed? Maybe it's time to upgrade to a new(er) machine.