Model A1419 / Late 2012 / 2.9 & 3.2 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac13,2

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Apple STUMPED - iMac shuts off randomly, daily to multiple times/hour

iMac 27" 3.4 GHz i7 (Late 2012)

This iMac was my father's and began having this issue last summer. It will simply power off completely at random - sometimes being able to be powered back on immediately, sometimes not turning on for an hour. This problem persisted for months and grew more frequent until it was happening several times a day.

Rather than try to deal with it over long distance, I had him buy a new iMac and took the old one with me to NYC. Took to Apple, who found nothing wrong.

I reformatted the drive, did a new install and step up with new software in a completely new environment - I did NOT restore from any user or backup. Within a week the Mac started shutting off again.

I brought it to Apple again. They kept the machine this time and ran diagnostic over days but could not get it to repeat shut down in their possession and insisted it was a software issue. We rebuilt the machine once more and tried again. This time it worked for a few months before starting to shut down occasionally again. At first just every few days, then nearly daily (oddly often around the same time in the afternoon), and then multiple times a day.

I brought back to Apple once more and eventually spoke on the phone with a master tech somewhere in the Midwest who also thought the "Geniuses" must be missing something and gave them more stressful test to try. Again, they can't get the machine to replicate the problem.

  • This machine has been rebuilt several times.
  • This machine has been in two completely different environments, with different sets of software from different sources.
  • I have swapped power cords. I have tried different surge protectors and outlets.

I am at a loss and Apple will not tell me anything is wrong to replace.

Except for the shutting off, this still remains one of the fastest Macs I've used from probably 15 different 27" models from 2010 - late 2015.

Any suggestions? Thank you very much.

Answered! View the answer I have this problem too

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I replaced the Power Supply for 125.00. Works great now. Apple has been no help in this issue.

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I’ve been dealing with the same for 5 years. Apple never finds anything wrong, get it back, still shuts down. Now they are whining about us requesting a new computer, on their dime, because of the age of the computer. My argument is that it has done this since 11 months old, now about 5, and I have almost never been able to use it during that time. They deny they have ever heard anything like this, yet I can find it all over Internet forums. I’m so frustrated! I’ll be purchasing some kind of crap laptop this coming week. I need a computer. But I’m done with apple products. (Even 3 of our 5 iPhones do the same thing).

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I had this same problem for the better part of 9 months (sometimes I'd get 5 shutdowns in an hour, and other times my iMac wouldn't shut down for days/weeks). Nobody on the forums I frequent had any solid ideas/suggestions about what might be causing this (I heard errant programs, kernel panics, etc., but none of those seemed to be the case).

Then I happened upon this article; lots of similarities to the problems I was encountering with this very specific iMac model.

I replaced the Power Supply about 3 weeks ago, and haven't had one shutdown since. At this point, I'm going to cast my vote for this being the problem/solution.

Word of caution: when peeling off the old adhesive from the back edges of the screen, don't be too aggressive. I applied a little too much pressure with my plastic widget/tool (don't know what it's really called), and wound up scraping off a little bit of the black paint on the backside of the screen, which leaves the glass bare (and noticeable when the machine is put back together).

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I had this problem and lived with it for about 3 months - I had the power supply replaced and it corrected the problem.

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Replacing the power supply board at Apple repair fixed my random shut downs.

I've been dealing with this for about a year.

~$220AU for power supply board instead of a ~$950AU mother board. Dodged an expensive bullet there.

Too bad I had to put up with it for a year. With hours and hours of support calls.

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11 Answers

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This is usually indicative of a partially failing power supply.

iMac Intel 27" EMC 2546 Power Supply Replacement

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I've replaced the power supply and hope that has fixed it for good.

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@billymoon well is it working?

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Yes, it is working. Because the issue of the Mac shutting down sometimes took weeks or months to begin happening, it will be a while before I can 100% confirm that the power supply was the issue. But looks good so far! Thanks.

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Fantastic and you didn't have to pay through the nose to Apple ;-)

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And did this now solve the problem? I am having the exact jouney... :(

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Since this is a basic first step to resolve power issues, I would imagine that the Apple techs have reset the SMC, but if not try this. How to reset the System Management Controller (SMC) on your Mac

I once had a similar problem with an iBook, many years ago. Resetting the SMC would work for a period of time and then the powering off would happen again. I discovered eventually that it was a logic board/processor issue.

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Thanks for the tip. The very first guy who looked at it in VT said the same. I though taking it to Apple would be best, oops.

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I do still have a problem because i cant reset the SMC. My Mac, when trying to power on he has the black screen and makes just one 1 second of that opening noise but then it stops. If try it again it even doesnt make the sound and shuts down instantly. I tried to unplug the mac to restart the SMC but it has no effect. Need help

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Mine was solved by replacing the power supply.

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After speaking to an IT guy who was having the same problem, I replaced the power cord and am no longer having problems. I also turn my iMac off at night and disconnect it from the outlet.

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I am having the same problem. I immediately thought it was the power supply and took it to get it replaced. The geniuses could not replicate the problem and told me nothing was wrong. I brought it home. It worked flawlessly for about 6 weeks and then it starts cutting off again at least once a day. When it cuts off, I have to disconnect it from the outlet and wait 24 hours before it will cut back on. If I leave it in the outlet, it will not cut back on. (Its a 27 in iMac I've had since 2012).

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unplug from back of iMac count to 30 (not 20).

Press power button for 30 (not 20).

plug back in count to 30 (not 20)

then you can power up as normal or in safe mode or in diagnostic mode, etc.

Won't fix your intermitent shut down issues but I was able to boot for about another week.

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Sounds like you have building (home) power issues!

Check your outlet is properly grounded and the breaker panel to ground is in good shape. You likely need a good UPS as well.

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I had the same issue with my iMac 27" late 2012 model, random shut down, pull the power cord, wait, plug back in, runs fine or a while, repeat every few days until it became daily.

I replaced the power supply board and it's all good... Only a few days so far with no problems for a REAL proof, but it was shutting down daily.

Key things?

I think the fact that I had to unplug after every shut down to be able to restart was a solid clue that it wasn't a software issue.

As Greg Blair pointed out, I ALSO have UNGROUNDED power to my machine. Maybe that is what kills the board? Just mentioning it here in case that turns out to be a common clue as well.

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Yes, you want a 3 pronged outlet which is correctly wired. I would also get a good surge suppressor or better a UPS!

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Yeah my problem was uncovered after I realized that in my 100 year old house, my three pronged outlet was actually just wired up without a ground wire. So It looked legit, but didn’t have the added protection that these sensitive electronic components require. Check your outlets especially in older homes!

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I have the very same issue. And the partial solution is the same too - power off the mac, remove the cord, wait a bit and start up. I've standard EU outlet though with proper ground.

What is weird is that this issue occurs during summer season, so when the temperature in the room is higher. I was suspecting that mac is maybe overheating.

I checked the logs and was not able to find anything pointing out to the overheating though. Actually, it seems the shutdown is very sudden leaving osx without any chance to write anything.

I started having this issue last year. I opened up my mac, cleaned up, checked all the components but didn't find anything obvious. I've decided not to use the adhesive strips on display but rather used the duct tape. I actually like the look ;) And as I also had to repair the crappy stand I think it's best to be able to open it any time.

New PSU seems a bit pricey for this old machine. I'd like to know where the problem is but as it takes time for problem to show and it's hard to reproduce I guess there's not much else to do ..

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Hm, my 2nd comment got marked as inappropriate -- I pasted output from system.log.

I wanted to share my experience with extensive testing I did today. Long story short: memory was ok, full ATH didn't report any problems.

More I forced the system to boot after sudden poweroff more unstable it was. I observed the same behavior under Windows 10.

SMC does report the cause of the previous shutdown though. From cmd line run the command "log show | grep -i applesmc" . There will be shutdown cause displayed. 0 means power failure, 5 means proper shutdown. Not very intuitive, but those codes can be googled out.

All the sudden issues are 0s in my case, so this is very likely PSU issue.

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I hope you fixed your homes wiring too! If you have missing or a bad ground that will damage the power supply.

Make sure the breaker/fuse panel ground is also in good shape! And use surge suppressors for your system and peripherals.

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I had this exact same problem with my Late 2012 iMac 27" i7. Must be something particularly sensitive with the PSU on these models.

Anyhow, I replaced the PSU with a new one ordered from Amazon (http://a.co/hXgDH0S) and so far so good! Upgraded the HDD to a 1TB SSD while I was in there!

So what causes these faulty PSUs on the iMac? I had no problems with this iMac until I started taking the unit home from work and plugging it into an outlet that was UNGROUNDED. I suspect that the fluctuations in current, be it sags or spikes, created this problem. I only did this under 10 times, but the damage was done.

Word of caution to anyone who has a failing PSU on their iMac.... check to make sure that you are strictly using a grounded outlet (even better if you equip it with a UPS with AVR) once you get your faulty PSU replaced!

Update (05/07/2018)

I still contend that the random shut downs are due to faulty power supply unit inside iMac.

Once these get tweaked by sags or surges in current from your electrical or ungrounded outlet the damage has been done!

I HAVE had a faulty logic board on a previous machine but it was exhibiting different behavior.

In my experience, when the logic board fails you see strange colors and picture on screen. When the machine just shuts off, I believe that is not a logic board issue and rather a PSU problem.

Apple is no help in getting this resolved.

Thanks to the iFixit guides and a little online shopping I fixed the issue 100% myself (and I’m no hardware guru, I’ve only opened up my iMac once).

Check out these attached pics of a failing logic board and you will see that that is a separate issue. If your Mac is randomly going black, shutting down and the only way to hopefully power it back on is after you leave it unplugged for a few minutes.. You, my friend have a faulty power supply!

Block Image

Block Image

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Grounding & power fluctuations will kill any computer!

Yes! you need to get your outlet fixed as well as make sure the breaker panel ground service is properly grounded and the ground point is in good shape (over time it tends to degrade).

You should have all of your peripheral devices on surge suppressors as a minimum. Or better yet should get a good UPS if you are seeing flickering lights or have brownouts.

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I brought my late 2012 iMac to Apple today and it powered down twice while I was there.

Power supply was one of the possibilties they cited.

Will let you know in "5-7 days" what they find out.

UPDATE

They replaced the power supply - just got it back today.

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@homerfrizzell - did it work for you? Any more shut downs? I'm having the same problem for about 6 months now...

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@hervoa - no shut downs since I got it back a week ago. I think the power supply was the culprit.

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Good for you! I just dropped my imac at an apple store to change the power supply. Here goes $200... :(

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I finally decided to drop it at an apple store. They kept it for 2 weeks and of course couldn't reproduce the shut down. I told them about the potential issue with the power supply - that i was ready to change. They checked every components (...so that they told me) but couldn't find any faulty hardware. So they basically didn't do anything - only cleaned it up, as dust was building up in there. Anyway, just got it back a few days ago. No crash yet....but still, Apple has to be aware about this issue. I even showed them some videos on youtube, showing the shut down!! they can't ignore this one forever...on a $3K box!!!

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Where do i start, my imac (2008) does the same (shutting down and back on again) i have changed the power chord and delved in and changed the power supply, that did nothing !!! I wiped the drive clean and a fresh install, nothing happened, so i put a new hard drive in, and still the problem keeps happening :( changed the ram, still no fix, so im only left with changing the logic baord !!! But after all that ive done, i dont think i can be bothered !!!

Update (03/22/2018)

so, well ......... I have just bought the logic board and I will be back with an update to tell you if it has fixed the problem

Update (03/22/2018)

so, the logic board arrived, I had to put the graphics card from the old board on to the one that arrived as it did not come with it and then installed the logic board and .................... it fixed the problem of randomly switching off and on, its running like a brand new iMac !!! I just wished I done that in the first place lol

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I know this is an old thread but I’d like to share my experience.

I had a very similar problem where my iMac would shut off randomly. Turns out the RAM was bad, I replaced the RAM and have been stress testing the machine for four hours using the “yes > /dev/null command and GPuTest. So far so good.

Be sure to try removing RAM sticks as part of your trouble shooting process. By the way, the RAM is Crucial 1333MHz 4GB x 4 sticks.

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Ok had the same problems like everyone I change the power supply

and replaces the memory.

I also changed the power cable and now have the system plug into its owns surge protector

It’s was still shutting off then I went back and l replaced the memory aain and now it has not randomly shut off in weeks.

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Just shut down completely every time you dont use your Mac and pull out Power supply over night. Worked for me. No more shut downs.

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My 2104 iMac have same issue too!

I’ve had to move to a country with 110 V, before my iMac have never had this problem under 220 V power of my home country.

So I’ll try to connect at 110 V to 220 V Transformer. That fixed the problem!

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Your power supply has in fact two circuits one for 120 volts and the other 220 volts. So your 120 circuit is bad! You still need a new power supply to fix this correctly. The cause was bad power! Do make sure to get a surge suppressor or better yet a UPS.

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Billy Moon will be eternally grateful.
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