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Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac12,2

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Shutdown and immediately restarts

Hello there!

Excuse the bad grammar, I am dutch myself.

When I click the power button of my iMac it turns on just fine, but when I am at the desktop it randomly shuts off (withing 5 min, sometimes longer sometimes shorter) and immediately restarts to do the same thing again.

Sometimes when I leave it at the desktop it stays on and just works fine (browsing the web, accessing the finder etc…) until I shut down the Mac myself, only to repeat it the whole thing again when turning it on.

I was wondering if this behaviour is indiciative of a failing power supply? I’m not seeing any other graphical glitches and or io faults so I hope it’s not the logic board. I could also replace the hard drive but it boots into the desktop flawlessly everytime, so I’m also not sure if that’s the problem.

To summarize: sometimes it stays on and works perfectly until I turn it off myself, most of the time it shuts down within 5 minutes after booting and sitting on the desktop and then immediately restarts.

Thanks in advance!

I would also like to add that it seems work for longer when it’s been turned off for longer, implying it might be something overheating inside. How can I maybe verify?

Answer this question I have this problem too

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Boot up, hold the "D" key on the keyboard, until it asks to select a language, and run the hardware test. This will tell you if something is failing.


This gives me a spinning globe, and a drop down menu where I can select Wi-Fi around me. Eventually it stops spinning and the mouse will not respond implying it froze up. It doesn't turn off though.

I can also confirm that the problem is not due to overheating, as I was able to install temperature monitor applications during the period it stayed on. I tried with a new hard drive, but the issue persists which also excludes it as the culprit.


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Android 维修工具包



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1 Answer

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Most likely a failing power supply. If the restarts have gradually increased, this would confirm it:

iMac Intel 27" EMC 2429 Power Supply Replacement

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I'm not sure gradual increase would be correct. If I leave it alone for a longer period of time, it stays on for a longer time as well the next time. When it starts shutting down it stays on the next time for shorter and shorter times.

Also when the iMac was installing sierra on a new drive I put in, it didn't turn off once. Also when booting it into OSX utilites (holding command + R) on boot, where you can choose disk utility, time machine and reinstall osx, it does not turn off either, it stays on just fine.

I appreciate your thoughts.


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