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

I"m having the very same issue with my late 2012 model 27 inch iMac and am SO frustrated! Apple had it for two weeks and "couldn't replicate the problem" which is bull, since it was crashing on ME every few hours. Geek Squad ended up doing system restore and it has crashed once since getting it back yesterday. This late model 2012 imac is clearly a lemon and Apple refuses to deal with it. I spent almost $3 k on it and it's just a fancy paper weight now. This isn't an event, it's a pattern. Apple you suck.

same thing here, and yes, only have had problems since Yosemite upgrade.

I believe the lack of response is due to these machine's being out of warranty - over 2 years old. They don't care. I'm sure a firmware update would fix this though and maybe 10.11 won't be such a dog of an OS.

I have managed to get some work done by unplugging the computer whenever I can; overnight, lunchtimes, etc... This definitely helps the machine work longer without crashing.

I am also one experiencing the same problem with my iMac.

iMac 27" (late 2012)

Yosemite 10.10.5

2,9 GHz Intel Core i5

16 GB 1600 MHz DDR3

NVIDIA GeForce GTX 660M 512 MB

I have had this ongoing issue for more than 5 months and been in contact with Apple Care, and they seem powerless, not wanting to deal with a known problem. I will try to get it replaced in one way or another as it´s been in and out of service without any results. Having spent hours re-installing and formatting the system and YET nothing changes I urge everyone with this random shutdown issue to contact Apple and or Apple Care. If many address the same issue surely they will have to act in one way or another!

Adding my machine to the ongoing list. Please note I have an active Apple Care Warranty.

The issue began 4 weeks ago. Apple Hardware Test diagnosed a bad ram module (all components are stock). Genius Bar session 1 replicated the error and made the same diagnosis -- RAM was replaced. Within 2 days, the system continued to intermittently shut down requiring a SMC reset. Genius Bar session 2: kept the system for 72 hours to replicate the issue. Issue was replicated and Apple is replacing the logic board.

As many have expressed, although Apple appears to at least recognize this being an issue for my system, I am very concerned this is a cascading issue. If the issue continues following a logic board replacement, I am hard pressed to believe replacing a power supply, HD, video card, etc will resolve the issue.

iMac 27 (Late 2012)

3.4 GHz quad-core Intel Core i7

8 GB RAM 1600 DDR3

1 TB Fusion Drive

NVIDIA GeForce GTX 680MX

I Had my iMac looked at for random shutting down and was told it's a bad video card and there was a recall on it for 2011-12 models. I have to find out if mine is covered.

I believe that was specifically to do with AMD graphics chips on the older 2011 - 2012 iMacs. This could be a similar issue though with Nvidia graphics cards instead.

https://support.apple.com/en-gb/HT203787

Quick update...

Updated by Genius Bar representative that they were unable to replicate the intermittent shutdowns using their power cable and they will run the same series of tests using the power cable I provided.

This information is completely contradictory to what I was informed of less than 24 hours ago. That being, the shutdown issue was replicated and the system is being serviced for logic board replacement.

The representative understood my concern regarding this contradiction, and will attempt to determine if the issue was in fact replicated. He also suggested they may replace the logic board regardless of what is determined.

I'm glad the hardware issue was replicated, and your machine will be serviced.

About your concern that initial information you received was "completely contradictory." I think many are in your situation are in a similar quandary. For some, it's a software issue, the logic board, a faulty fusion drive, or something else. I hope you'll post back with your results.

Hi, I have had a very similar issue with my late-2012 27" iMac and have been following along here for a month or so.

27-inch, Late 2012

3.4 GHz Intel Core i7

16 GB 1600 MHz DDR3

NVIDIA GeForce GTX 680MX 2048 MB

Fusion Drive 1TB

Since I bought the system in early 2013 there were a few times my son had some freezing issues playing 3d games but never anything that wasn't fixed with a restart and I just wrote it off to driver problems or issues with the game.

Mid-summer this year I began to experience the system locking up with video artifacts filling the screen(small red and green squares mostly, sometimes others). It would happen during any system intensive task such as video editing or rendering, photoshop work, etc. 99% of the time I would have to reboot manually and even then most times the system would refuse to reboot, hanging with a few light graphic artifacts appearing during the grey screen with the progress bar. Resetting PRAM etc would not help and going into hardware diagnostics would not report any issues (even though the Hardware Diag. screens would occasionally have graphic artifacts or flashing colours themselves) The only thing that seemed to get things running again was leaving the the system off for a while and then rebooting. Over the course of a month I tried just about everything - different video drivers, installing the El Capitan beta, reinstalling a completely clean OS etc - without any any luck in resolving the issue. The odd time a panic log was generated it seemed to show the video drivers were the source of the problem.

I eventually found I was able to replicate the problem 100% percent of the time by running GpuTest's FurMark. As soon as the GPU Temp reached 70-80 C the system would hang with extensive video artifacts etc. It seemed like a classic case of a GPU or video memory failure due to a solder joint, very similar to the issues the led to the 2011 Macbook GPU replacement program. Everyone I consulted said that logic board replacement was my only option. Unfortunately it is not under warranty so the cost would be extremely high. I ended up pickup up a new iMac just so I could keep working, figuring eventually I would get the logic board replaced so I could sell or repurpose the system (and probably hoping Apple would announce a replacement program).

Now the interesting part - Wednesday I had some spare time so I replaced the El Capitan beta on that system with a clean instal of the full release version. Since then the system has been on full-time and I cannot replicate the issue at all, either through normal usage or running GpuTest/other system stress tests. FurMark has been running on that system almost constantly during each day with the GPU temp hitting 90-93 C. Occasionally when I stop and restart the test there is a very brief graphical glitch for a split second and then the test runs fine. Other than the updated OS the only thing I can think may be a factor is that the system had been turned off for 4-5 days before the El Cap install.

Any thoughts? If the issue does come back I will post an update.

Further Update:

As in my last update, a Genius Bar representative informed me that they were unable to replicate the intermittent shutdowns. However, I inquired as to what tests are being performed as well as what diagnostic information they are attempting to gather. They informed me that the OS logs each time the system is shutdown (manually or unexpectedly). With each documented shutdown, there is a code that identifies the reason. The logged code associated with an intermittent shutdown is what they were after in the attempt to replicate the problem. I wish I had asked this question earlier...

While on the phone with the representative, I immediately isolated a date and time during which I experienced an intermittent shutdown. He was able to locate said shutdown in the OS log. He looked up the associated log/code and determined it was related to a sudden/unexpected loss of power to the system. As the system has been used in the same outlet along other devices (i.e., electric cycling training, a laptop, external monitors, etc), this finding appeared to lend some support to a faulty iMac power supply and/or system power cable, and not the environment in which it is used.

Apple Support is now replacing the power supply and providing a new system cable to remedy the situation. I should have the system back this week, and I will update with any additional findings.

I wish users would follow your advice analyzing and poring over these iMac issues. Moreover, I believe that the Apple representative probably made the correct diagnosis by replacing the power supply.

However, the vintage of your machine apparently makes it potentially vulnerable to this problem. You probably know that a trip to the Apple Store won't fix it forever. That's why aggressive heat management may be your best long-term solution. These high-end iMacs really generate heat, and it can concentrate in vulnerable areas like the logic board, graphics board, hard drive, and power supply. During gaming or video rendering, heat can come close to 200 degrees F. At the least, these temperatures can weaken solder and flux.

Several applications can alleviate heat problems. I use iStat Menus, but there are several other options - a few even free. Never allow your temperatures to rise above 165 degrees F for any reason. If the temps rise too high, increase the fans to compensate. Don't assume that your iMac will do it automatically.

>> Hi, I have had a very similar issue with my late-2012 27" iMac and have been following along here for a month or so.

Sorry, I just realized I had meant to submit the post referenced above in a different thread more related to my video issues with the 2012 27" iMacs. It doesn't have much to do with power related crashes but it does not seem I can remove it. C

I am another victim of iMac 27" Late 2012 random shutdowns which neither Apple Store nor a Premium Reseller are able to replicate the problem in order to find a solution.

I have tried and done everything with no solution

HD test passed with no problem

Reset SMC everytime the computer shuts down which is something very frustrating and annoying

Install OS

Files and software not original removed and the shutdown keeps happening (NOT A SOFTWARE PROBLEM)

1 visit to apple store and they could not see what the problem was because the computer was working owell there

2 visits to premium reseller with the same conclusion and to my surprise their are not even concerned about this magical shutdowns

(I am thinking about having an office in an apple store where I can go to work with mi imac because in my house is impossible)

I think Apple cannot avoid these posts, this discussion is taking place in their own official support forum. There are plenty of cases like ours and Apple is ignoring us.

Exactly my situation.