Why is my imac shutting down by itself?

But what is the feature and where do i find it?

http://support.apple.com/kb/PH13914

Cheers, Not sure what to do now to stop it from shutting down on its own. Can you help me a bit more hehe sorry to be a pain.

go click schedule on bottom right corner.

Thanks. Nothing seems to be ticked in the boxes, so maybe it was just a glitch.

I posted something a month or so ago because my new iMac was randomly switching itself off. I tried the various suggestions and also reinstalled OSX as Apple Support suggested. After they took it in to have a look, it worked fine for 14 days and then it started happening all over again - including shutting itself off in the middle of reinstallation. So I took it in again and finally it apparently switched itself off in front of their very eyes (so they believed me!) and they said it was the power supply which they have now replaced. Last Tuesday afternoon they send it was in transit back to the shop - but since they put it in the wrong place for the courier to pick up (it was Express Service) it took three days for it to travel the 50 km from Utrecht to Leiden! And I picked it up this afternoon and have spend the last few hours reinstalling the software and my backup of documents and files. Since all the instructions on the computer were in Dutch, I called Apple Support again (at premium rates!) for assistance - luckily they were working on a Saturday!) and they helped me - however, in another twist to this sorry tale, when I gave them the repair number they informed me that my iMac was actually an iPhone according to their bit of paper (though not according to mine!). Anyway - let's hope it was the power supply inside and that the problem is solved - certainly deleting the power management configuration file nor setting the display timeout to never didn't help. And I think we probably proved that it wasn't the software or anything in my files!

jojoSour wrote:

Hello All,

I finally contacted Apple and took my computer into the Apple store. They ran a diagnostic test and found out that the hard drive was bad. SO they kept the computer overnight and replaced the HD for free, since I have Apple Care, otherwise it would have cost $265.00.

I'm writing this only two days post-replacement, so I'll update you if the problem has NOT been resolved.

On a side note, a friend of mine with the same computer had her HD crash on her a few weeks ago. Apple replaced that as well, but she never had the shut down issued that I spoke of.

Thanks for posting back . This was more helpful for me than possibly you might think.

katiex0x wrote:

... It just might be a design fault. A friend told me it sounded like the automatic shutdown in the Energy Saver setting wascausing the problem so he said move it to Never, which I did.

No problem since, but this isn't a good fix for those who like to have their computer turned on for long periods. Good luck fellow sufferers! Nothing else I tried helped, but this did.

See Rick Deckard's solution above. Corruption of a .plist file is a far more likely reason than a design fault.

Far easier to fix too.

Today Apple finally decided to replace my power supply here in Brazil. Let's see how it goes...

A new 2014 iMac fresh out of the box started shutting down randomly. Had to restart as it would not wake up. At Apple's suggestion, we reinstalled the OSX from the Recovery partition and it has not happened again since.

Apple replaced my power supply here in The Netherlands on 1 July (as previously reported). Well I am experiencing the same problem as before, namely that the computer suddenly switches itself off for no apparent reason. I can only bring it back to life by pulling out the power cord and leaving it unplugged for about ten minutes. It first turned itself off on 13 August (i.e six weeks after repair), then again on the 28 August (it had been unused for ten days in between those dates), then again on 2 September and again just now on 3 September. I have never ever had such problems with a new (or even old) computer!!!! If the thing would save work it would be better - but it doesn’t and thus you lose everything. I have contacted Apple - so we will see. It is clearly something to do with the power - maybe the fan is overheating and it switches itself off for safety - but who knows!

Everyone posting in this thread is saying their computer is shutting down. Is that what is really happening?

I have a January 2007 24" iMac which has never had the problems described -- until about six weeks ago. But the computer is not shutting down. If I put my hand where the startup button is on the back lower left of the machine, I can feel that it is still on. I am assuming I am feeling the fan operating. What seems to me to be happening is that the computer is going to sleep and cannot be awakened. I have found no pattern up until the last several days, as the problem has continually gotten worse. I, too, brought the machine to an Apple Store, but they could only run the "light" diagnostic tests on it because it is over seven years old. (By the way, talking to Geniuses these days is like talking to Best Buy sales clerks. Didn't used to be that way. If I ever did what one of the Geniuses told me to do, I would have screwed my system up really badly.) Their suspicion was a software problem. So I did and erase & install. I then reinstalled only my really necessary software. Made no difference at all.

I used to leave my machine on all the time. After a while with this problem, I started shutting it off at night. I now have to start and restart it several times in the morning before it will stay on. (But of course I never know when it will "go to sleep" again.) And when it happens throughout the day, I sometimes have to retsart it several times. Sometimes when the problem occurs after a restart, the machine will actually restart again by itself.

It is beyond my comprehension that a problem this serious that has been going on for this long cannot be identified and solved by Apple. I am losing all the faith I have had in the company since my first Mac purchase in 1992.

"2. Delete the file com.apple.PowerManagement.plist"

Tried it. No difference.

Probably a heat, caused by dust, problem. Try blowing the dust out of the system.

But how could it be heat if the problem occurs immediately on startup after the machine has been off for ten hours?