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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.

Is your machine connected to a UPS by chance?

I'm not sure. What's a UPS? And in case I still don't know what that is after you tell me, how can I find out if I'm connected to one?

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.

Have you reset your SMC? This can help sudden shut downs:

 

  1. Shut down the computer.
  2. Unplug the computer's power cord.
  3. Wait fifteen seconds.
  4. Attach the computer's power cord.
  5. Wait five seconds, then press the power button to turn on the computer.

jojoSour wrote:

 

I'm not sure. What's a UPS? And in case I still don't know what that is after you tell me, how can I find out if I'm connected to one?

I think you answered my question, a UPS is an Uninteruptable Power Supply.

 

Try BGreg's solution and report back what you find.

Ok, so I tried this solution, and I thought it worked, until it didn't. My computer went about a week and a half before shutting down as I was using it (today). So I tried again. Keeping my fingures crossed. Thanks again. Any other suggestions?

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

What peripherals do you have plugged into the computer? I suspect one may be the problem.

The only things I have plugged into the computer are a WD external hard drive, speakers (which sometimes were playing music, and sometimes not playing when a shut down occurred) and a printer that is off 99% of the time.

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.

Did you ever get this issue resolved through AppleCare?  My imac does the same thing - shuts off randomly!  I've had this imac for about a year & 1/2 and didn't purchase any additional warranty plan so I would love to know what the solution was for your problem.  I have no peripherals attached except for speakers, like you. 

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?

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!

Out of curiousity, did you happen to have any new memory (RAM) installed on your computuer?

最后更新：2017-09-05 00:42:03

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