Any thoughts on why my iMac has been randomly shutting down and trying to reboot but can't. All started with Catalina. when it does reboot I often get the message your Mac shut down because of a problem. If it is shutdown for a while it will reboot otherwise will stop part way through.
The next time it shuts down unplug the power cord from the back of the unit, plug it back in and reboot immediately. Are you able to?
If so it could be a failing power supply. Test it repeatedly on subsequent shutdowns so see if an immediate boot is possible after unplugging and plugging in the power cord.
Hi thank you for the reply. I wish it were that simple. I've talked with apple support and worked through doing different resets but with no change. I guess the nuclear option of removing and re installing Catalina would be next. do you or anyone have any other thoughts ? My concern is this seems to be a common issue with Catalina and that re installing wouldn't change this. Thoughts?
iMac shuts down randomly. I have to unplug from AC an plug back in... only way I can turn it on. Grey screen comes us first few seconds, then the Apple bar with sign in. This only started this week, iMac is only 5 years old. OS X Yosimite 10.10.5, intel core 15. Thank you
That's indicative of a failing power supply. Had the same problem on my wife's iMac. It would not restart with the power button unless I unplugged the power cord and then plugged back in.
You need to make sure you have a current and full backup of your boot drive. In my dealings with Apple they had me erase the drive and then reinstall the system without any of my user files. This was to make sure it was a hardware problem rather than a software one.
If your local Apple store has reopened you can make a Genius Bar appointment for a free diagnostic check. It it's determined to be the power supply they will replace it for you. However, you'll probably have to pay for it as it won't be under warranty. If the Apple store isn't open you can probably find an Apple Authorized Service Provider nearby that is.
Bottom line, you might want to erase the drive, install pristine system without any of your files and run to see if it still shuts down or not. You'll have a good idea where to go from there.
Thank you. I have an APC power tower (for when electric goes out) gives me time to shut down.. the iMac is plugged into that. Could it be that OR does it have to be the iMac power supply? I've had to replace a power tower before, though it shows battery power is fully charged. Just a though?
losttechworld wrote:
Thank you. I have an APC power tower (for when electric goes out) gives me time to shut down.. the iMac is plugged into that. Could it be that OR does it have to be the iMac power supply? I've had to replace a power tower before, though it shows battery power is fully charged. Just a though?
Unplug from the APC and run from the local power supply for a while to see if the problem persists. If it does then we can rule out the APC.
From what I've gathered here in the forums it seems more prevalent in laptops. The only shutdown I've experienced is due to a bad power supply.
iMac randomly shuts down then cannot reboot
