Why is my imac shutting down by itself?

"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?

Well mine has just switched off again after five days. I have taken to switching it off at night and also when I am out for a while during the day. I have also turned off putting the disks to sleep etc - and I thought a combination of all this had maybe done the trick - alas obviously not! It doesn't seem to like being on longer than six or so hours at a time. And when it switches off, I cannot bring it back to life by just pressing the on/off switch - even after leaving it for an hour or so. I can only restart it by pulling out the power cord and leaving that out for a while.

I don't think it's anything to do with dust. My older machines have sat on the floor for years without complaint - and this new all-in-one iMac sits on the desk. True, sometimes it gets a bit of sun on the back of it - but no enough to cause it to overheat.

Robert Golden1 wrote:

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

... 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. ...

That's not a reason, that's an excuse. A pretty poor one too.

I reckon that they knew darn well what the problem was - that your iMac needed new parts, probably something on the main circuit board, because that's where most stuff is. I think that they simply didn't have the moral integrity to tell you that the main circuit board your machine was irreplaceable because the main circuit board isn't manufactured anymore.

Mind you, one could probably say the same thing about any iMac greater than a maybe six months old. Not that knowing this will be of any comfort to you, of course.

It's a ploy common to most manufacturers of nearly anything these days. It used to be rife in the automotive industry until consumers started to getting wise. It's known as 'Built-in obsolescence'.

Actually, everyone was very clear about the fact that parts are generally not available for any Mac older than seven years. That was the reason they could not log the machine in and run the more comprehensive tests.

I have the same issue. I have trawled through everything written on this that goggle identifies without a single solution. I have tried everything suggested in multiple posts on similar topics without success. I have tried everything suggested by the geniuses at apple. It seems it is a hardware issue. My recommendation is to immediately take to It back to apple as it could and probably is a hardware issue that only gets worse and worse over time. Reinstalling OS, SMC and PRAM issues, third party software and peripherals hubs etc are probably not the issue. After reading multiple post the problem only reappears and becomes more frequent which indicates to me that it is hardware. Why does anyone need to prove to an apple genius it is hardware let them prove to you it is not hardware. Don't waste your time especially if it randomly occurs!

Mine is a brand new (well, January 2014) iMac. Worked three months then started switching off. Not software as Apple first thought, turned out to be faulty power supply they eventually said and replaced. However, same thing happening again now. But it seems that after several hours on (whether I am working or not), it seems to get hot at the top on the back - and then it switches off. I can only switch it on again by removing the power cable and leaving it out for a while. If I don't wait long enough after plugging it back in again, then it often switches off again rather quickly - presumably because it is still too warm inside for it.

I might have just discovered a lead that I am in the process of chasing down and will report what I find out. Up until today, there has been absolutely no consistency whatsoever in when the problem occurs. As a matter of fact, I was operating another iMac using a clone of my system and the problem didn't occur at all. I therefore concluded that it has to be a hardware problem and not a software problem as the Apple genius suggested. However, today I have run into it with 100-percent consistency using Safari 5.1.10 when going to www.scottsdalefilmfestival.com . Every time I go to that site, the screen goes black. I am trying to find out what possible plugin that site is requiring in the hope that it will give us a lead. Of course, that would contradict my conclusion that it is hardware and not software.

I finally got my new iMac back yesterday - the Express Service took three weeks and one day. They ran Apple Diagnostics (again) and this time found "multiple errors on the processor" and ordered a new logic board. When the new board came, they tested it and found that it was defect, so they ordered another. After testing that, they deemed it was OK and installed it in my machine. As the computer is still under warranty (it is only a few months old anyway!) then I didn't have to pay anything. The shop people were very apologetic and agreed I should have a new machine if this one starts shutting itself off again. So I suppose that when they replaced the power supply earlier, it should have been the mother board. We'll see what happens in a couple of weeks!

This has been driving me crazy. I hope this works. Will try it out as soon as I get home! Thanks.

I have it too since several months. The MacMini I have is shutting down every time I go away for a couple of minutes (toilet, whatsoever).

My guess that it is an implemented bug to oblige people to buy a NEW Mac, that's how most unethical companies work these days: Not the quality is important but the number of objects sold and… avoiding it last far longer than the usual warranty period (the extra payable warranty period is of course included).

I would be more that happy if anyone can tell me the exact opposite and thus… a way to avoid this annoyance.

Especially because I have a very large FileMaker database which need every time to be rebooted (due to the IMPROPERLY CLOSED issue) which takes more than 5 minutes to be executed. In other words: I do not only have to wait till the Mac has started up, but another 5 full minutes to wait till the recovery is done.

And I only have to leave it 2 minutes (TWO MINUTES !!!) and it has shut (improperly) down!

It's a 2.4 GHz Intel Core 2 Duo with 2 GB 1067 MHz DDR 3 running under Mac OS X 10.6.8.

Furthermore as a disabled person having only a few minutes free a day (yes, A FEW MINUTES, all else is surviving stuff… in which I NEED the computer), I can't afford to visit this site every time again, so please send me a reply to danny "." lauwers3 "@" telenet "." be (yes, without the quotes and without the paces.

Thanks you so much for every support you van give me. My "free" minutes for today are already consumed. Thanks for respecting me, understanding me and giving me advice ONLY about this issue.

I.e.: everything considering my health is perfectly "under control" and improving during the years.

DLWorldCitizen from Belgium, which capital is Brussels not the other way round, dear fellow Americans :-)

This seems to be working! 8 hours and no shutdown.... praying.

Sounds like a RAM issue to me. Have you tried reseating the ram. I had a similar issue with my 2011 IMac. Crucial exchanged my Ram modules and problem disappeared not to return.

Since I last posted on here (17 Oct) my iMac (now upgraded to Yosemite) has been behaving itself - so I guess the original problem was always the logic/mother board.