Why is my imac shutting down by itself?

I, too, have been plagued by the unexpected, random shutdowns I've experienced since July 2013 (after my computer was opened up for repairs). I have a 27" iMac, late 2010, 2.93 ghz i7 quad, 16 gb ram, on 10.6.8.

I had no problems with the computer, which is basically an image workstation, until July 2013 when I noticed slowing performance. I took it to the Apple store in Houston, and they diagnosed it as bad logic board, which had fried 1/2 of my ram. I had the board replaced, and a few weeks later, the shutdowns started. At first, they were spaced apart far enough that I wasn't losing much work. Later, they were more frequent and frustrating, so I took the iMac back to Apple and left it there for 3 days for diagnostics. I was told that the hard disk was showing errors, so I had that replaced at my expense. Apple also replaced the logic board again at their expense. Same result - a few weeks later, the shutdowns began again. Normally, these occur when the computer is awake, and I normally have LightRoom and Photoshop open, and Safari. Sometimes a lot of data is being crunched, and other times the unit is not under demanding processes.

I avoided taking the unit back to Apple during the holiday madness, so I went back in January 2014. One of the geniuses thoroughly went over my use of the computer as he ran tests. We looked at the Console, and he had some suspicions about connected peripherals, especially my Wacom tablet. Apple agreed to replace the video card, and I picked up the unit about 10 days ago.

I unplugged the Wacom after the last repair, and had a shutdown on 1/31. I reloaded the latest Wacom driver, but had a shutdown 02/08, and it still was unplugged. I unplugged all USB items except my mouse, and had a shutdown 02/09. Only my Burly tower with external drives is connected by FW800. A older Cinema 23" is connected for my palette monitor.

I've checked the power cord, and other items plugged into the UPS do not falter when the iMac shuts down.

If my understanding is correct, if it were to be a power supply problem, I could not re-boot after a shutdown. I can re-boot immediately.

I've lost so much productive time with this iMac and the time and money lost while it is at the Apple store.

Latest update: the Apple Store called me 48 hours later and said they just think that it was a loose connector on the display. Doesn't make a whole lot of sense to me, but I said ok and went to pick it up, at no charge. Since then, I have brought it home and it has been on ever since, hasn't shutdown once...but I am keeping a close eye on it. Will update in a week or two and let everyone know if I am still having any problems. I asked for more details on the disconnected "connector" but they didn't really have any.

Hello. I have a iMac OS X 10.7.5 and it keeps shutting down randomly by itself. It started doing this in january 2014 and i don't know what is causeing it. I took it to the mac store and they ran a complete assesment on it. about 2 weeks later they called back and said that they couldn't find anything wrong with it. Note that since they did not take in my computer to "my" power cable that i was useing "I assumbed" it was the power cable itself, so i got a brand new one. My computer wasn't turning off as much then but i wasn't using it as much ether. but now it is back to shutting down back itself more frequently again.

When I took it into apple they said they never saw it shut down by itself and that they found absotulty nothing with with my RAM, logicboard, screen, Nothing.

I'm checking to see if there is something wrong with the circit breaker in my house but nothing else seem to loose even a few seconds of power.

I write this out of fear of my mac shutting down again, so forgive be if im blunt and have bad spelling or grammer

the link to download it no longer exists

Are you referring to the link to iStat Pro? It's been discontinued, however, CNET has it here,

I had a client with an iMac that randomly shut down several times a day. After trying many things, the solution I found was this:

1. Go to Library/Preferences/SystemConfiguration/

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

3. You will have to authenticate with an administrator password to trash the file

4. Reboot the computer

That's it! No more shutdowns after using this procedure.

Hopefully this will help someone who's having this issue.

That method seems to be working, thanks :)

My five month old iMac started shutting itself down a month ago. It was not possible to restart until I'd unplug it and plug it into a different outlet (I was desperate). This kept happening so I took it to the Apple Store and they were unable to replicate the problem. So back home I went and soon my computer was having the same problem. So I asked for a replacement iMac and Apple provided it. No sooner was I home with everything transferred to the new iMac than the problem resurfaced. I even plugged it into different circuits in my house and suffered the same problem. 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.

Same happening here. I am thinking that maybe Lightroom have something to do with it. It looks like Lightroom makes the temperature rise a lot.

I live in The Netherlands and bought a new iMac earlier this year. After three months it started shutting itself down for no reason and the only way I could get it back was to pull out the power cord, plug it back in and press the on/off button at the back. After a few days of interuptions, I called Apple Support and we did some various checks. Sometime later, it switched itself off again - it didn't matter whether it was idle or I was writing an email or whatever - infuriating, especially as emails were not saved. Apple Support then had me erase all the data and reload the Mavericks. That didn't make any difference. So I took it to the shop and they sent it off to Apple who returned it a few days later saying they had checked all the hardware and reloaded the software and it was all fixed. However, I was expecting a system similar to when I first bought it - pretty much ready to go. But they had loaded up some Dutch version and I had to go on top the internet and download and install Mavericks again and then restore my data and files. The computer worked fine for two weeks and then it started switching off again last week. I tried deleting the file powermanagement.plist as suggested above - but the next day it shut off again several times in succession. I am hoping they will give me a new machine as this one clearly has a major problem - maybe to do with temperature (though I am not sure what Lightroom is) or power or something in the system software. It is VERY irritating because I simply cannot trust the machine.

If you iMac is still doing this. Go back to Apple and ask for a new Mac. Its clearly faulty!

My iMac has been doing this for three years. Apple doesn't seem to want to acknowledge or address this problem. It's impossible to use the system for work, because I can't afford to have it shut down in the middle of a project. Nothing seems to make any difference. I've tried all the posted fixes. They don't work. It has nothing to do with software or timing or anything I can discern, except maybe my moods!! I'm beginning to think the thing shuts down in response to some fluctuation in my own bio-electrical vibrations. 🙂

This worked for me!!!!! I thought I was going to have to reimage my system. Such an easy fix. I recall changing the setting a few months ago and suddenly the problems started happening, but would only happen when I walked away from my Mac. It became frustrating when I would stream over AirPlay and I'd have to wake up my Mac all over again. So glad its working now.

Much appreciated!

It worked for five days - and now it starts again. Apple Support want me to do a clean install and see how that goes. I will have to put back my docs though - but won't do any of the config files. We'll see!

Any news, people...? I'm desperate. I simply can't work.