Why is my imac shutting down by itself?

Awesome, this fixed my problem - thank you so much.

Glad to hear. Unfortunately, my imac continued having issues. Ended up buying a monitor and using my macpro as my main computer. Boomer. 😟

Am I glad to have found this thread. I'm not alone!

I have a 15.1 model (Retina 5K, 27-inch, Late 2014) with 8gb of stock RAM. Im running 10.11.3 El Capitan. I do not have anything plug into it.

The first time it powered off, I had selected a bunch (over 1k) photos on my ext. HDD and I was "Heart"ing them. My ext HDD lights went off. To get it to power on again, I had to unplug the power cord to get it to turn on again. I also suspected it could be my extension so I moved it to a different socket (didnt help. Eventually I used a totally different wall socket with no changes). After rebooting, I continue again to do the same work. It powered off again after a short while. I thought maybe it was the memory.

Normally I use the iMac to just surf using Safari. So for one week after the initial episode, nothing happens. But now it is powering off while it is in sleep mode. Its is also powering off once while I was surfing uisng Safari. So far it had happened to my iMac for about 7-8 times and the interval in between failures is getting more frequent

My warranty is about to expire in 10 days. Im wondering if I should quickly get the ACPP but looking at some of you that had got power supply, logic board, etc replaced and still with no changes to the problem, I dont know what to do. I have only read till page 9 of this and its late here so I will continue tomorrow. I just want to chime in to report my machine.

Hi everyone,

I got the news that Mac Pro had the same issue, it was related to the graphic card, causing those computers had video distortion, system instability, restart andshut downfor no reason, or affect to system boot. The affected models meet the requirements,Apple will provide a maintenance service for free. I think our iMac had the same issue in same reason, hope Apple will provide something to fix that problem.

Oh, how about static electricity? Did you guys heard about that?

I've read something for discharging the static electricity, said to unplug all connection of computer, press and hold the power button for more than 10 seconds, that's it!

I'm just trying this way, hope it works!!!

I tried this and it works but it keeps happening

Same thing happens to mine IMAC (RETINA 5K, 27-INCH, LATE 2014) only 7 months old

Had the power supply uint change ,last week .

got it back, after 6 hrs the mac shuts off . back too the same problem .

its like having a power cut .

only way to start the dam thing is to pull the main plug out of the socket

Its back with apply authorise dealer. still they cannot find anything wrong , i told them to play 4k videos .

the diagnostic test they run does not pick up errors, as i did with over the phone with apple , but when i was on the phone with apple support he mention to press Command + g to run safari and to play a video .

so i went on youtube and play a 4K video , and thats when it shut down again in front of the Apple support Guy on the phone ... its hardware problem

I am another who's been affected by this dreaded curse.

My late 2012 imac 27" has been repaired with and both the power board and logic board have been replaced over the past few months. Yet still, the imac switches itself off.

Currently undergoing diagnostics but the engineer isn't experiencing any power outages with my system.

This has to be one of the most frsutrating experiences of my life. Been withou the imac for over 2 months over the past 6 onths and my business i ssyffering as a result.

Will never buy an Apple product again after this.

This happened to the last two iMacs I bought, starting in 2013. What worked was cancelling or making very lengthy the period of time when it would reduce the power draw. My iMac would go dead and I had to keep plugging it into different electrical outlets to turn it on again. That was what worked. I have good, steady electriucal power, no surges, so it is a problem with the computer.

John B.

I have been following this thread for a while. I had a look at "About This Mac" then "System Report" then "Power"...... The graphic below shows what I found.

Even though my iMac is not configured to auto power off or on in the Energy Saver preference I notice that it has an AutoPowerOff Delay of 14400. If that figure is minutes then that is 240 hours or 10 days. If it's seconds then it's 4 hours. I can't find any way to change these amounts. It's a long shot but given that no-one has mentioned it, it may be worth investigating.

Interesting find, but doubt that is it. Sometimes mine will shut down, start right back up and immediately shut back down.

I have had the same problem with my iMac 2014. I have been dealing with Mac support for nearly 6 months. Hours of calls and countless hours of re-installs.
I have tried cleaning my hard drive, re-installing OS and apps. I have tired different ram, I have tried different power outlets. I have brought it into the store now just recently for the third time. This time they replaced the processor and the power board. Freeze. Shut Down. Same thing. They are sending me a new iMac. I hope this resolves it. Not sure if there is a design flaw with thunderbolt connections? As an editor I do have an array of drives plugged in. Might try without anything plugged in, but then that is not the way it is intended to be used. EXTREMELY FRUSTRATING. Customer support always very helpful/kind but still, come on. Something's not right if many others are having the same problems.

Hello all, count me in, i also have an IMac thats shuts down of its own accord and also won't turn on unless the power chord is removed . I have read most of the posts and nothing suggested is working, i have come to think that it might have something to do with the mouse. I use TurboCad for technical, drawing at times when i get two or three fingers slightly on the mouse it can send the drawing spinning off into infinity, do you think that the static that builds up on the mouse have something to do with the problem?

I have been through the genius route and also the experts who work for the company that sold me the IMac all with no success, i have a screenshot of the moment it last happened and this is being looked at by the company expert, i don't think anything will come of it. In the meantime this is very frustrating i lost hours of work and drawings last week. What can we all do? I have been told that even though my warranty has lapsed i am protected by consumer rights and could possibly get another computer to replace it, this only if the problem is found, and also a long way off i feel

Count my machine too... So frustrated.. Can't rely on Mac these days.

Good news today my Mac has not closed down, thinking it maybe heat i have turned off a desk light that i have right next to it, so far so good, will keep you posted

I am wondering if you perhaps stumbled onto the solution, or at least a part of the solution. My thoughts are that is it possible that the infr-red pickup used for the remote control may be getting :jumbled" info that it sometimes interpets as a shut down command or something similar? If so, turning off infra-red may give some people the cure.

Here, from the Help files, is the way to turn the infra-red receiver on (or off).

Turn on IR reception

Choose Apple menu > System Preferences, click Security & Privacy, then click General.

Open the General pane for me

Click the lock icon to unlock it, then enter an administrator name and password.

Click Advanced.

In the window that appears, deselect “Disable remote control infrared receiver.”