LATE 2012 27 inch IMAC Power Off Randomly

OK, it just shut itself off again... problem not solved with fans.

Every computer problem like this is a little different, with different causes and solutions.

In this case, you determined - rightly - that the problem won't be solved with fans.

By elimination, it's likely to be one of two problems: (1) failed Fusion drive or (2) the power supply. You can investigate both, but it will require a little discipline. If it's a failed Fusion drive, the drive may be covered by a program from Apple that you might be familiar with; if your machine isn't covered, I'd still lodge your complaint with Apple Support. The problem may be more widespread than Apple thought..

It could be the Power Supply, however...but you can figure that one out more easily. Power Supply problems are quite predictable. If you get a shut down, say, after four hours use, reboot; the next shutdown will be under four hours. If you're still connected, the next shutdown will happen even faster. Troubleshooting a Power Supply problem requires discipline. Document whenever your computer is powered, and how long...and whenever you get one of those shut downs. Leave your machine on all day, if necessary, and determine when the problem happens. If it's a Power Supply problem, the shut down will happen.

Kaleb, make a genius bar appointment and take your iMac in for service. You obviously have a hardware problem that needs attention.

Sometimes it shuts down after 10 minutes, sometimes it's right after log in, sometimes it's after 20-30 minutes.

I scheduled a genius bar appointment today, but trying to perform a full backup has taken the entire day since it keeps shutting itself off. Sometimes it's even during a file transfer, so I've had to make small file copies manually instead of using Time Machine for automated backup.

In that case, I look look forward to the results from the Genius Bar appointment. Please post with the results.

I'm betting it's the HDD portion of your hybrid drive, based on the information you've provided. The drive swap isn't complicated, and that's good news.

This time Apple replaced the display and logic board.

However... after 1 day, the problem returned... when I tried running it overnight, it had shut itself off by morning.

Appears to be the exact same issue... after one of these shut downs, it won't power on again unless I pull the power cable out for 15 seconds... and the moment it's plugged back in, it boots itself up without even pressing the power button.

This will be the third time I've had to take this 27" iMac in for service for the exact same problem... what a huge disappointment. Off to schedule another Apple Genius Bar appointment now...

I mainly use

Adobe Illustrator CS5

Adobe Photoshop CS5

Corel Draw X7

Also my main objective is to get the exact color on the I Mac which i want to print on offset printing

and good processing speed of Large Files which i use while designing.

Strange, i just suddenly started to run into this issue myself, i use lightroom 5, photoshop, illustrator, FCPX and then i do gaming on this 27'' iMac 2012 i.e.: Starcraft II, World of Warcraft etc when i got the unit in 2013 till about a month an half ago it would be fine. Recently it just starts to shut itself randomly for no reason i downloaded all the fan controls, istat nothing worked so i gave up and took it to the apple store. Tested it attempted to have the issue happen at the Bar of course it doesn't happen. They tested it and worked on it (also managed to break my display so i got a new one for free lol) handed it back to me said nothing is wrong. Got it home changed the power cord, the surge protector and moved it to a new outlet. (also to note i wiped the unit clean when i got home set it up with Yosemite with just the basic essentials) Boom again happens while playing video games or running my adobe products. Cant seem to figure it out anymore really frustrated with the **** thing while idle its at 1200RPM kicks in to 2784RPM when gaming or intense production. GPU goes to like 184-185F i noticed and shuts off randomly. Half tempted to toss this crap into the garbage and build a tower at this point since not even apple knows whats going on with my unit.

Hey Darkxres, you should ask them to try replacing the power supply.

It took me 3 trips to the Genius Bar.. they replaced the 3 TB fusion drive (a large number of seagate barracudas they used were defective, enough to start a replacement program just for that), logic board, and display... nothing fixed my shutdown problem until they finally replaced the power supply.

Hope that helps!

So the solution was in fact replacing the power supply?

I've just started getting random shut downs while I'm playing games—even then the internal temperature never got above 163. Like everyone else the solution to get my iMac back on is unplugging, waiting, then replugging. I thought power might be the issue—even thought I might test the outlet to make sure it has the proper voltage, but it sounds like from what your saying, the cord may be to blame.

HI Kaleb, any resolution with this problem? Having same issue.

Me too! 2012 iMac 3.4ghz. Pile of Junk.

I've done two support calls with Apple, dropped off at an Apple store to reinstall the system, then took to a local Apple certified repair shop, then back to Apple store for repair. The store said it was software related but now it's powering off unexpectedly again. So back to calling Apple. I've never had a problem with an Apple computer in the 15+ years I've used one. This is so frustrating.

I have the same machine, same situation. I'm convinced at this point it is the power supply as I've already replaced the 3TB fusion. Each shutdown is under load, GPU/CPU and spinning up of hard drive to launch programs or manipulation of graphic assets. I'm going to try the power supply fix and I'll report back......

I have the exactly same Late 2012 iMac 27" with the same issue, started since this May.

It randomly shuts down. I guess it's shutting down because screen blacks out suddenly, all usb stop powering my iPhones, mouse and trackpad and keyboard no responding, and has to be unplugged for 15 seconds and then able to be re-powered on, which procedure is pretty much the same with resetting SMC.

Before that whether short-press or long-press the power button would be in vain, it does't respond.

I am also guessing it's a power-supply issue. Since my iMac is already out of warranty, I have to make sure and only pay for the real solution, I can't replace everything to find out what is the point.

Is it possible to become a free replacing program if enough people encounter this issue?