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

This thread helped me pinpoint my problem, hopefully I can return the favor. My problem was ultimately Firefox and Flash which led to heat related shutdowns. Even after I replaced the GPU.

Here is what worked for me:

- opened Firefox and added the Add-On 'Flash Disable' (Tools>Add-ons>Get Add-ons)

- I also uninstalled Flash from my computer. (easy steps via google)

- in Firefox I disabled Hardware Acceleration

'Preferences > Advanced > General > Use Hardware Acceleration When Available

Un-check that.

- added SMC Fan Control, keeping fans at about 1300-1350 RPM and temps at 113F/45C

- restart. Its been good since. And loads much faster on startup.

Here's the backstory to see if your machine might be doing the same thing.

My 2011 iMac is a 27" i7 with the 6970 AMD Radeon graphics card. Apple gave free replacements of this card since it was a known problem. So when the iMac started shutting down randomly, I discovered that recall. No more Apple Care and I was WAY out of the window to get this done for free, but the Genius Bar honored the recall. (They agreed I wouldn't have looked for known problems if I wasn't having any. So how would I have known the card might go bad?)

Before discovering it was the GPU I tried all the resets, diagnostics and safe mode, including trying to reload the OS. In the middle of the reload it shut down. Blinking folder icon from then on.

So Apple loaded El Capitan after they replaced the GPU (with the same problematic brand/model as before but that's another thread)

Apple confirmed all was well with their tests. I took it home and reloaded from my TM backup. 5 hours later it completes, I log in and within 30 minutes a prompt comes on the screen 'Are you sure you want to shut down?' and even though I press 'Cancel' it shuts down. It does this a couple more times while I'm trying to get to the bottom of it and then stops asking altogether, just shutting down intermittently. The only thing that can get me back into the iMac is the SMC reset. And even then for small periods of time. I ran the Hardware Diagnostic and it shut down just as it was testing the logic board. Fantastic.

So all of that to say, it looked like it was the same problems as this thread. Below is where I started in my fix. Some steps may be unnecessary, but it's what I did. It has been running for several days now with no problems.

This assumes you have a backup.

I started from scratch:

- unplugged from the wall and let the computer cool down overnight.

- in the morning, pressed the power key BEFORE plugging it in. (read this might discharge the capacitors?)

- CAREFUL HERE MIGHT DO DAMAGE - To check the logic board I removed all the RAM, plugged into wall, pressed power. If your computer starts beeping supposedly this means the logic board is still ok. (mine beeped)

- held power to perform hard shutdown. UNPLUG from wall. Re-seat RAM

- plug into wall, press power, reset PRAM, at second boot tone, quickly switched to Internet Recovery (command option R)

- went into Disk Utility and performed First Aid, verified and repaired permissions. They were fine. Then I erased my drive. Went back to Internet Recovery and reloaded Lion. (I could not do this while having El Capitan on the machine. You can go forward with OS versions not backward. At least easily.)

- then I reloaded my machine from my Time Machine backup. This will take several hours. And ultimately, I still had the problem of random shutdowns, just not as frequently.

- Then I proceeded to the steps listed at the very beginning.

I don't know if I could have stayed with El Capitan and just changed my Firefox and Flash settings, but for now I'm just happy to not have to re-visit the Apple Store. Hope this helps.

Another late 2012 27" iMac with 2Gb Nvidia, 1Tb fusion drive. I installed 16Gb of Crucial RAM in 2013 after purchase. I've also stayed on Mountain Lion until this problem where I upgraded to El Capitan. Reading this thread... seems this is a depressing problem to have as very few cases of a proper fix.

Not sure what to do as before coming to this thread I assumed it was a power supply problem, but with so many having had that replaced and no change then I don't know what to think.

Joining the party from Turkey. 27'' i7 3.4 GHz, 680MX, 32GB original Apple RAM, 3TB Fusion. Symptoms started a little after the 2 years of warranty window ended. I thought it was because of the hard disk back then (which Apple replaced for free). Took the iMac home but since then I was using the laptop a lot more so I did not notice or the problem did not replicate itself for some months after the hard disk replacement. Now it is shutdown fest.

One interesting bit, I've been told by the Apple rep on the phone that I should try to set up a new user and leave it on and try to see if it shuts itself down. So far it is working. Tho mostly idle.

Just for the new ones: The most "working" solution that came up in my research is disconnecting the iMac from power completely when shut down. I did not experience the problem since I religiously do that (which is annoying because you cannot simply shut down and go, but hey, better than nothing). Please try that and pray it's working for you, too. 🙂

Exactly. Unplugging helps, but it doesn't change the fact that due to this issue, we're forced to live with "random shut down anxiety" every time we're performing critical tasks and/or using the computer over prolonged sessions.

Overall, in this thread, the only hopeful solutions we've seen so far are:

1) Getting Apple to give you an entirely new computer (only works for people who are still under Apple Care and undergo three unsuccessful repair attempts).

2) Someone earlier talked about not using Apple power supplies (since even the replacements seem to be defective), and instead using a totally (more powerful?) 3rd party power supply. Have any tinkerers had luck with this yet?

3) Not a permanent solution, but there was a guy much earlier in the thread who had something hooked up between the power cord and wall outlet that behaved like unplugging the computer, but only required shutting down to have the same effect. Is this an effective workaround to physically unplugging?

For what it is worth my late 2012 imac with a non fusion disk has just started to have exactly the same problem. Come on Apple at least look into this and come up with a chargeable fix at worst, your processes missed this manufacturing defect with the late 2012 imac.

Hi everyone,

This morning, I was watching videos when I had to go to the kitchen check some food. When I came back, my imac 27 (2012) was shut off! I was wondering what happened then. So I tried to switch on with the power button in the back, but it didn't work at all. I felt very stressed at this moment because my applecare is over since March, and the PSU had been replaced on february, so I guess it's not linked with PSU. Anyway, I managed to reboot the Mac, by unplugging the power cord from the wall, waiting a few seconds, and plug it again. Then the power button worked again, and I was able to use the computer again. I won't switch it off now, because I'm afraid the problem occurs again. So I only use the sleep mode.
What is the cause of this problem? Planned obsolescence?

Your issue went away when you stopped using Safari? That's weird because I don't use and never have used Safari yet I still have random shut-downs.

iMac (Retina 5K, 27-inch, Mid 2015)

3.3 GHz Intel Core i5

8 GB 1600 MHz DDR3

AMD Radeon R9 M290 2048 MB

THE RANDOM SHUTDOWN PROBLEM STARTED HAPPENING TO ME ABOUT A WEEK AFTER MY 1 YEAR WARRANTY. I DID NOT GET APPLE CARE BECAUSE I DID'NT EXPECT TO HAVE ANY REAL PROBLEMS WITH THIS COMPUTER. MY FIRST TIME EXPERIENCE IS VERY SIMILAR TO MANY OTHERS FROM THIS THREAD. IT SHUT DOWN RANDOMLY AND I COULD NOT TURN IT BACK ON RIGHT AWAY. AFTER UNPLUGGING IT, WAITING A WHILE AND PLUGGING IT BACK IN, IT TURNED ON. HOWEVER THE SAME PROBLEM OCCURRED NO LESS THAN AN HOUR LATER. I DID SOME RESEARCH AND FOUND THAT "PREVIOUS SHUTDOWN CAUSE: 0" MEANS THAT THERE WAS A POWER DISRUPTION. I BROUGHT MY COMPUTER TO THE APPLE STORE ON THE UPPER WEST SIDE OF MANHATTAN AND TOLD THE GENUIS THAT IT WAS PROBABLY A POWER SUPPLY PROBLEM GIVEN THE SYSTEM LOG CODE. HE SOUNDED LIKE HE AGREED WITH ME. AFTER A FEW DAYS WITH THEM, THEY DIAGNOSED THE PROBLEM TO BE WITH THE LOGIC BOARD. I PAID $721 BUCKS TO REPLACE THE LOGIC BOARD. I USED IT ON JUNE 21ST (THE DAY I GOT IT BACK) WITH NO PROBLEM. THIS MORNING ON THE 22ND, I EXPERIENCED THE SAME RANDOM SHUTDOWN. I UNPLUGGED IT FOR ABOUT 10 MINUTES AND TURNED IT BACK ON. I LEFT IT ON FOR OVER 3 HOURS ON SLEEP MODE, CAME BACK AND I HAVE BEEN ON IT FOR ABOUT 6 TO 7 HOURS.

TO ANYBODY HERE, IF THERE WAS A PROBLEM WITH THE LOGIC BOARD WHEN WE EXPERIENCED THESE RANDOM SHUTDOWNS, THEN WHY DOES THE SYSTEM LOG INDICATE THAT THE PROBLEM HAD TO DO WITH A (POWER DISRUPTION ISSUE) AND NOT ANYTHING TO DO WITH THE LOGIC BOARD?

WHY HAVE SO MANY OF OUR CASES BEEN DIAGNOSED AS LOGIC BOARD PROBLEMS FIRST WHEN THE MAJORITY OF THE TIME, THIS ISSUE HAS TO DO A POWER PROBLEM?!?!?!?!?!??!?!?!?!??!?!?!?

Wanted to follow up on this.

I first brought my iMac (27-inch, Late 2012) 3.4 GHz Intel Core i7 NVIDIA GeForce GTX 680MX 2048 MB 1 TB Fusion into Apple for repair last month, they kept it for a week and said it was the SSD failing which is part of my fusion drive, and charged me $500 plus to fix it. Pricey, but problem solved, right? No.

I got it back, problem persisted. I took it back in.

Very thankful that on my second visit I got a knowledgeable and helpful genius who knew right away that the SSD was a misdiagnosis of the problem. He refunded my $500 and told me that he was almost certain it was a power supply issue. He also repaired that for free since they wasted my time the first go around.

I've had the computer back for about a week and so far so good (though, only time will tell). This is what I've concluded:

This is a HARDWARE issue. I refuse to believe that we are all using some special combination of software that could be causing this issue when we all have the exact same model of iMac.

My advice is take your computer into Apple, show them this thread and that it isn't an isolated issue. Have them repair your power supply first, which is the cheapest of the repairs I've seen (around $150 at my Apple store).

I assume the log entries are just showing where the problem occurs and not why the problem happens. In my case its a software issue but I have the exact same problem of what you describe. Just when I stop using Safari I dont have it anymore. It seems to work just for me but you can see the variety of the problems is huge and in the end its always that random shutdown problem.

Another one here!

iMac (27-inch, Late 2012)

3,2 GHz Intel Core i5

NVIDIA GeForce GTX 680MX 2048 MB

After reading the 21 pages of this post I've no solution yet 😕

I hope anyone can find a solution. I think I'll try to change the power supply by a non-original replacement.