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Why is my imac shutting down by itself?

I have a late 2010 27in iMac and it has shut down randomly by itself 4 times in the last month or so, including twice in the last couple of days. I have 16G of RAM and am only using up to 8G ever. Just to be clear, it shuts down and does not restart automatically. I never have the screen brightness higher than half so I don't believe I am overheating it? I really want to know why this keeps happening.

iMac (27-inch Mid 2010), Mac OS X (10.7.3)

Posted on Apr 10, 2012 5:15 PM

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Posted on Feb 2, 2017 3:42 AM

I am having an issue with my iMac 2011.The screen keeps shutting down.It turns black so often that even before it logs in it will turn off.I have this problem since July 2016 and I have brought this iMac for repair for 5X.The last time was this December 2016.The apple technician will say a lot of different issue from the logic board, power supply, software problem and LCD screen.They seem not to fixed the problem.I really doubt apple capability to fix this problem.Funny every time you go to this particular store at friendly center and check my iMac, You will second doubt yourself because they will say they did not see any problem.So several times I need to go back again reassert my point.I am going to bring this again for the six times and see what happen.One thing I am sure if they can't fix this " I will never buy any apple device ever ".I taught it is worth all the hard earn money you put on this device because of its reliable.I paid for the repair and they never get it fix.So I will keep you posted people.

265 replies

Dec 4, 2017 5:17 PM in response to jojoSour

Wow. How helpful was the post from the member who said: "check your power cable." 😝 Idiot I am, the main power cable into the back of the iMac was wobbly, not pushed in. No more problems!

My 2010 soldiers on, deficient in RAM (I'm sure) but a sturdy performer. Put in a new hard drive 5 years ago, at my guru's suggestion, not SSD, and it moans/groans/heats up, but never disappoints.

Apr 10, 2012 6:04 PM in response to jojoSour

Have you tried wiggling the AC power cord at both the wall socket (or surge protector bar)? You may possibly have a bad socket. Is anything else also plugged into the same surge protector preferably something that would stay off if its AC was interrupted. A light would not do since it could just barely flicker while that interruption would shut off the computer.


You may want to try it on a differnet AC power circuit. This would be a different breaker (or fuse) circuit from the one you are normally on. Is the AC outlet or circuit running on a ground fault interruptor protected circuit and if so, does the GFI trip? Coul;d it be reset by someone else if it is not right at your desk area?


Does this happen when you are using the computer or when it is just idling?


Is your preference setting to NOT start after a power interruption? You may want to, just for the heck of it, toggle this setting (In Energy Saver) on and off to see if it will result in a restart? If so, start looking more deeply at AC power problems.


Is there any particular program you are using when this happens?


Are you on some type of network where someone else could be getting control of your system? (Apple remote Desktop allows this kind of action.) If so, updates may have been remotely installed which will cause a restart or shut down if that is chossen by the remote administrator.


Has everything been fully updated? Some updates will shut the computer off for a restart. This is especially true for EFI type updates. This usually results in a restart which is not what you said was happening. Instead you got a shut down to a cold start. If that is the case then the updates are not the cause of your problem.


It is also possible that you could have a power supply failing. Are you still under three year AppleCare? If so give them a call to put the problem on record in case it develops to whare you need hardware repairs.

Apr 22, 2012 4:04 PM in response to Joe Pyrdek

OK Joe,

1. Switched power sockets, but it still happend.There are a few other things plugged into the same surge protector, but they did not power down when the comp did.

2. It happens when I'm using the computer.

3. It was not set to start up after a unintentional power down, so I changed it.

4. It seems to happen when I'm using Safari, but I'll have mulitiple programs idling at the same time that I'll switch back and forth to. Thus, the beauty of Lion

5. The network I use is secure, and although I have remotes with my iPhone and iPad, I am not, nor is anyone else, using those at the time of shut down.

6. Everything is updated

7. I have AppleCare, and will contact them tomorrow in case the power supply is faulty.


Thanks for the suggestions

Apr 22, 2012 5:05 PM in response to jojoSour

OK then what I recommend doing is another SMC reset and then unplug and leave unplugged each peripheral 1 at a time until you have determined it is or is not the problem. Because your the last SMC reset worked for 1 week this may take quite some time, try leaving each unplugged for at least 2 weeks. I am assuming the printer and EHD are USB devices and the speakers plug into the speaker output plug and all devices are plugged directly into the iMac meaning you are not using a USB hub.

Jul 16, 2012 12:12 PM in response to minainCA

No I sure didn't. I ended up moving to a new place, and was hoping that it would stop after I tried a new outlet and new surge protector. I also tried a full SMC reset as instructed on Apple's support page (and a previous post). It has been about 20 days since I set up my imac and the random shut down has only happended once or maybe twice. But I noticed that it seems to only happen while I'm on logged on to Facebook, even if I'm not actually using safari at the time, but its open and on the FB page.


Anyway, I need to notify Apple officially, so that it's documented and if it continues to happen, hopefully they will replace whatever is busted. That's why I have AppleCare right?

Jul 16, 2012 12:17 PM in response to jojoSour

Thanks for your response. I can't see any correlations between the shutdowns and applications in use for me. Good luck to us both! I'll be sure to post here if I figure something out. Yes, definitely use that AppleCare! OH, by the way...you don't think it's a virus, do you? My husband suspects this and won't let me download any music from a source other than itunes now!

Why is my imac shutting down by itself?

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