Why is my imac shutting down by itself?

I have had the same problem! Mine is a late 2012, 27" iMac. It happened once in about January, then again around March, then twice in April, once during a recording session. Up until that time it had been great. I took to the Apple store- all hardware checked out, but they replaced the power supply and reinstalled the operating system (have been running 10.9.5 since it works with Protools 10 and the Waves Bundle I have doesn't work on Protools 11- I wanted to finish out some sessions before moving to 11).

Got different ram and I also replaced my power surge protector and got one that auto-regulated 120V. It was great for 2 months- thought it was fixed. Then it happened again- I was running nothing at the time. They replaced the logic board. Took it home and it hung in for 2 days. Ok- cut to the chase- everything was replaced, all factors isolated, 5th time to the "genius bar" and it is still not fixed. Yesterday I had them wipe it clean for the second time and I picked only certain applications from my time machine backup to put back on it. Brought it home and it stayed on for about 2 hours- then down again.

I finally said screw this- I'm losing money and ordered a new one.

I don't get why Apple can't find the issue. I'd at least like to be able to sell it and recoup some money toward the new one. They aren't cheap.

APPLE- WHAT'S UP????

Hi All,

I am back here after almost 2 years now. My 27" 2012 Imac was experiencing the problem discussed here. I left the system almost unusable for about a year, trying variety of experiment with in OS level and other soft were which I regularly using. I did nothing in the hardware department. Strangely for the last one year it works perfectly, not even a single shut down (unexpected) in my experience. I suspect the culprit is GTX 680 and it's drivers. I updated graphic driver along and OS to Sierra last year. I think this made the change to my system.

Regards

Rajiv

Howdy

I never did discover the cause or the solution. I suspected a heating issue, but then it would sometimes shut off when absolutely cold with no indication of any temperature rise from my monitoring utilities. It would definitely shut down when it overheated, which it would do when the graphics were pushed - gaming, Photos, even iTunes when scrolling through my hundreds of albums.

I could always count count on it to shut down when doing a file transfer from an external drive or a download from an online source.

I have read every thread I could find on the subject and most people have their theories. Every one of them has been acted on by someone and the fixes have failed - even total logic board replacements.

My solution was to wait for the new iMacs the past June and buy one. Ka-ching $$$.

Now my headache is being caused by the inability of the Migration Tool to see either Mac and my old Mac shutting down during manual file transfers. Yay.

If your old computer is still shutting down abruptly then its only future use is as a paper weight. So take your old computer to an Apple authorised service agent and pay them to remove the hard drive and put it into a case. Then you will be able to migrate your information to your new computer.

Is your machine connected to a UPS by chance?

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.

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

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.