LATE 2012 27 inch IMAC Power Off Randomly

I was battling this problem for over a year. Back and forth with Apple support, determined to show me it was a software issue. It went in for repair with Amsys in Dec 2016 - they found no issue having run the iMac for 3-4 days on end. They returned the machine and charged over £114 for taking a look.

The iMac was then relegated to the back of the office, for me to carefully debug whenever I had some downtime.

A few weeks ago an agent at the Apple store managed to find the issue after days of running videos in multiple tabs - a heat sensor was not working. It was hard to replicate as their labs run at a cool temperature. I presume their diagnostic tools are unable to determine whether a heat sensor has failed without the iMac heating up to the required temperature as every diagnostic tool in their arsenal had thus far come up blank.

Either way, I hope this helps someone else having the same issue. As the issue occurred months outside of the 3-year warranty, the staff I have spoken to appear keen to not fix this under Consumer Law. I can't tell you how frustrated I am to be told that it is run of the mill to have such a £2400 machine become unusable after 3 years. Replacing the logic board would cost over £600 or they offered a £300 trade in.

I have the same computer and had the very same problem. I also run Photoshop CS intensively as a photographer.

For me, they had to replace the power supply. It seems to have resolved the issue. I had actually read of other people on here with the same problem..but there are still not enough people claiming this problem to create a recall. I'm guessing you have the same problem. The genius bar person had seen the problem before..so it was the only thing we tried (and recommended not trying it on your own). With service it was about a $100 fix.

Good luck!

Hi Jenn714, did you solved the problem with your iMac? My late 2012 iMac 27" shuts randomly off and ik need to unplug the power cord and wait 5-10 minutes. I also brought it to an Apple service centre and they found nothing.

Sometimes I think could it be an Adobe issue. It's when i'm using Adobe CC.

Regards,

Bjorn

Hey guys, my Late 2012 imac i7 is having the same problem shutting off randomly and to get it back on I have to unplug it from the back wait 10mins or so and plug it back in

this been happen for a little over a year now I have been back and forth to the Apple Store they changed my hard drive my Power supply and I still have this issue. I have spoken to offer five senior advisers and I'm still having the same issue With the iMac shutting off. Please can anybody help solve this problem.

After 18 months of shutdown agony I was very frustrated. The local Apple Shop could never replicate the problem or find anything wrong with the computer.

In the middle of autumn here in southern Australia the problem became so bad that the computer was shutting down several times a day, including when it was asleep with no programs running or connection to the internet or to the Time Machine backup. It also used to sometimes die when I was shutting the machine down.

The straw that broke the camel's back was when it did that during a restart after a system update and corrupted the operating system so badly that Apple Support suggested I wipe the hard drive and reinstall the operating system from scratch. Even getting the existing information off the computer and onto a portable hard drive became a nightmare because the computer would abruptly shut down while I was doing it.

In desperation I decided to do what others have done and get the local Apple Shop to replace the power supply unit. Before replacing the power supply the local Apple Shop tested the computer again and still couldn't find anything wrong. One month later and I haven't had a shutdown.

If you are having this shutdown problem I would highly recommend that you try replacing the power supply first before spending money on replacing video cards, screens, CPUs etc.

You will probably have to insist that they do that first because they will still argue until the cows come home that it is likely to be one of the other components and not the power supply. Given how often replacing the power supply has solved people's shutdown problems that is not always true.

Hello, I had the same problem for months. I did not think it was a problem directly related to the power supply but rather to the ground. So I connected the screen directly to the ground with a simple crocodile clip, and for 6 months, no worries ... Can be a coincidence but in any case, it works perfectly.

Just the same issue happens for me. Imac mid 2015 27 inch 5K. The screen gors off randomly and imac dors not power on again. If I take off the main supply cord and wait a few minutes then imac opens ** pressing the power button and everything works. I made hatdware check (pressing 4 buttons during boot) and it says everything is OK. I have formatted the hard disk then made a clean install for high sierra. Worked flawlessly. But still imac shuts down randomly. Anybody any idea? Please help.

Kaleb - I have begun experiencing the exact same situation you describe on my iMac (Retina 5K, 27" Late 2014 with 3TB Fusion drive). However, when I click the link you shared, the Fusion drive replacement program no longer appears as an option. Do you know if this was for a limited time only, and otherwise how I can find out my options for getting my Fusion drive examined and/or replaced?

Thanks for any input you can provide.

It has been more than 1 month, yes 1 month since I have been trying to resolved this issue. I have an IMAC 5K Retina purchased at the end of 2014...It started going black. I brought it into Apple- they said they couldn't reproduce the problem. I left it there and brought it in my 2 external hard rives (1 time machine back up - 1 data)-they said it only shut down after a long while with hard drives in...but was ok with 1 drive. Their solution? That I should only use 1 drive at a time. Uh, did I mention that I am a photographer and also that this machine is made to hold up to 4 external drives. Anyway... I brought it home not knowing what to do. I worked on my computer without the hard drives and noticed that the display was now marred... in the bottom corners it was dark and fuzzy... which is not how I brought my computer in. It still was going black, powering off... if I unplugged and plugged back it and powered on it would go on - no error messages, it would just start and stay on for a short while before it went black again and powered off. I brought it back to the store, they replaced the display and wiped my computer. They told me not to upload and restore from time machine just in case it was a software issue. However, the IT person I work with remotely had me do that anyway while also creating a new user that was not attached to Time Machine. It lasted a day before it went black and powered off. Last year, they replaced the power supply, 2 weeks ago they replaced the display and last week they replaced the logic board. Today, after not connecting any of my external hard drives since it was picked up on Sunday, it powered off. It powered off on both users and luckily it is staying on while I am writing this. Also, I have been using my data external hard drive on my laptop with no issues... so not sure if it is the software on there... perhaps problem could still be caused by something that is being transferred by my 5 TB time machine? I had to be the bearer of bad results... but here it is... I am awaiting a call back from a senior analyst (again for the 3rd time) to advise me for the next steps. I am assuming I will need to wipe my computer yet again... and then... I don't know what's left to do.....? (as a side note, they upgraded my op system twice... first to El Capitan and then to Sierra....)

Try to have a look at this thread.

27 iMac (2012) crashes and requires smc reset to turn on

I won't request an Entrecheck report, since I'm pretty sure I know what the problem is. And how you might resolve it.

You're a graphic designer, so your machine probably performs some intensive projects. When your machine's temperature rises above a certain point, your iMac automatically shuts off. In fact, I can pretty much guarantee that the heat is concentrated on the CPU Cores and GPU Die.

The solution is to reduce the overall heat load. Using your machine intermittently doesn't make much sense as a means of reducing heat. But there are some good solutions. My personal favorite is iStat Menus http://bjango.com/mac/istatmenus/

Macs Fan Control http://www.crystalidea.com/macs-fan-control?ref=macupdate is said to be very good.

Ive been having system reboots and rampant application crashes happening for 5 months now and no solution in sight!

Someone mentioned power could be an issue but apples infinite wisdom tells me its not their HW is my SW I've installed for work... I'm a motion designer so its just cinema 4d and the creative cloud I'm using mostly... impossible its just something i have installed if my entire industry is not having issues.

The problem has continued despite 4 fresh reinstalls of the OS, a logic board replacement, new monitor display, 3 sets of ram and install of the SW for the fusion drive.

I spend 10+ hours a week with apple care (this week i dealt with 5 different senior advisors) and truthfully, my girlfriend is starting to get jealous i spend so much time on the phone with advisors.

Lxrcan,

I've got to admire your sense of humor in the face of a series of hardware problems and repairs.

In your case, it's certainly a hardware problem. Heat is usually inextricably bound with this kind of problem, but is seems - given the context of your repairs - that it's most likely related to the power supply. I'm hoping your motto is: "Heat down, fans up!"

Speaking of: your heat should never, ever rise above 165•F under any condition.

Do you have the 3 TB Fusion Drive? If so, Apple started a replacement program for these...

"Apple has determined that a very small number of 3TB hard drives used in 27-inch iMac systems, may fail under certain conditions. These systems were sold between December 2012 and September 2013. Apple or an Apple Authorized Service Provider (AASP) will replace affected hard drives free of charge.":

https://www.apple.com/support/imac-harddrive-3tb/

I can assure you, the issue is not the power supply. I had nearly all of the iMac 27" internals replaced under Apple Care before they knew what this issue might be, including the power supply. They even replaced my 3 TB Fusion drive with another 3 TB Fusion drive (even upgrading my system to Yosemite without my permission). Within months, the problems returned... and yet again, I'm trying to back up this system to have Apple replace the 3 TB Fusion drive a second time now.

My iMac powers off instantly by itself, with no heavy load, just sitting idle. It's completely cool to the touch — the fans are not going at all. The only way it powers on after one of these episodes, is to pull the cable for at least 10 seconds, then plug it back in... to which it immediately starts up without even touching the power button. If you don't wait for 10 seconds, it does not respond to the power button at all.

I do notice it seems to power off more frequently when it accesses the 3 TB Fusion drive. It is completely incapable of doing a Time Machine backup, as the instant power offs have affected it's ability to back up. The initial backup started quickly (it was transferring hundreds of MB per second, and the progress indicator said it would take about 8 hours) — until it's first instant power off during the time machine back up. Now, backups trickle in at no more than 1 KB per second. I have 1.5 TB of data to back up, so I have to do this manually between power offs. This is by far the worst mac experience I've ever had in my life (and I've owned/used 6 macs in my lifetime). My 6 year old Mac Book Pro is more reliable than this 27" iMac... it's such a horrible situation.

I just started using Macs Fan Control, to see if heat has been a factor in this iMac's sporadic and instantaneous power offs...

At start up the fan was at the minimum RPM: 1199-1200. Heat sensors report the following:

CPU Proximity: 105° F

GPU Diode: 120° F

LCD proximity: 104° F

Mem Controller: 97° F

APPLE SSD: 91° F

APPLE HDD: 111° F

After setting the fan to run at constant 2500 RPM for 20 minutes now, things have cooled down considerably:

CPU Proximity: 98° F

GPU Diode: 111° F

LCD proximity: 100° F

Mem Controller: 91° F

APPLE SSD: 86° F

APPLE HDD: 104° F

So far, running the fans at a constant rate of 2500 RPM seems to have stopped the automatic shut down problem.

I'm going to continue backing up with the fans running high...