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

Yes, I went through nearly the entire thread and perhaps unplugging it each night is a bit helpful. However, that is a side issue. The real issue is that this model/year is inherently defective and Apple is not acknowledging what for them would be an expensive problem to deal with. Instead they let us all flounder around looking for an answer between us. It is more than likely they already know what is causing the problem and the solution to it. Apple: If they ignore us long enough, we will go away in frustration. These are some of the best engineering minds in the world and to believe for a moment they are unaware of the issue or the correct fix is simply not believable.

It happened even with an imac 5k. I toyed around with some other ram and reinstalled the OS from scratch, wiping the entire drive, and it didn't restart in two months.

I have more imacs doing the random restarts and one had a bad thermal paste on so it was getting very hot and then restarted and the other was another ram related issue.

its very hard to put a diagnostic on it when it happens randomly. I did not get and kernel panic attacks in my logs, except the one that kept restarted because of a bad ram.

Yup mine is a late 2014 iMac 5k. Very intermittent but lately it got worse so I sent it in for repairs. One day had passed but the tech says nothing has happened yet.....duh! 😕

Btw mine is not restarting on its own but sudden power off. Cant get it to power on again until I pull the plug to reset SMC

I already tried unplugging every night and it work great for 4 days. On the 5th day, it powered off 4 times in a short interval and another 4 times the next morning in short interval. I thought its broke for sure this time and took it in.

This is a one month update from my posts dated 1-8-16 at 10:48pm & 1-19-16 at 8:12pm. After experiencing identical issues to everyone on this thread, the following parts were replaced by an Apple authorized technician on 1-19-16:

Main logic board

Power supply

Power cord

Hard Drive

After 30 days, everything is working well with no shutdowns or issues, knock on wood.

Now... after reading every single post on this thread since those dated May 2014, I have learned three important factors about this 2012 iMac and the shutdown problems:

1. The issue is NOT the logic board or motherboard. If you only replace the logic board and nothing else, there is a 100% chance that you will be back for more repairs within days or weeks. When technicians make this recommendation (to only replace the logic board), ARGUE WITH THEM! and refer them to this thread. This many people from around the world can't be wrong!

2. It is NOT an overheating issue or "excessive dust in the unit" problem. When my iMac was in the shop with the monitor removed, the technician noted that not a spec of dust was present anywhere in unit... and I own two cats and create as much dust as anyone.

3. It probably IS an issue with the power supply or a component connected to the supply unit. Recently, several people have noted that a bad capacitor could be the culprit... this remains a possibility also.

RECOMMENDATIONS:

1. Don't waste time with Genius Bar test... this proves absolutely nothing when attempting to diagnose the issue.

2. If the shutdown issue "can't be replicated" by an Apple technician, have them connect & re-connect devices to the USB ports in the back of the unit. Also, have them keep the machine powered on for several days and then put it under a stress test. Finally refer the Apple techniians to this thread. A good technician will not "ignore" this many people with the exact same iMac problem when this much evidence is present.

3. Call Apple and report the issues before and after an Apple technician has a look. Just having Apple document your issue with your iMac serial number goes a long way even if you don't have the Apple Warranty. Also, KEEP A DIARY of dates, times, events leading up to the shutdown. I did this in an earlier post and it was very valuable to both Apple technicians at the national database and my local repair people.

I have the same model and I had the same problem. But now it does not exist for me.

Just unplug your iMac from the outlet when not in use. I use a power strip with a switch for it.

I do not know why it works, but it works. No crashes and sudden shutdowns for half a year.

Hope this helps.

This is a very long thread and it may have been addressed but...are you all recording the Previous Shutdown Cause from the Console? You can do this by opening the Console app in your Applications > Utilities folder, going to it's search box and typing: previous shutdown. A number will be displayed. If it is a hardware fault, it will be a negative number. A normal shutdown is registered as a 5.

I think it's a good idea to do this because Apple doesn't publish the code descriptions anywhere but if you all list the code in your problem description, you may get an idea where the fault lies. For example, I had an iMac that was randomly shutting down, particularly when the graphic's card was stressed. However, I could immediately restart, no smc reset. All the previous shutdown causes were labelled -128. After doing extensive research, I concluded that this was a fault with the discrete graphics card. I actually fixed my iMac through a process of reflowing my graphics card and reapplying the thermal paste/pads(Long story). In the process of doing this, I also made sure that the connections on the graphics card were cleaned up AND that the pci-e slot on the logic board was also cleaned, thorougly, with a small scrapper tool and rubbing alcohol. I was surprised at how much gunk was in the pci-e slot, which could explain power sensing problems causing shutdowns. It would also explain why some people here may have their graphics cards replaced but the problem comes back later or vice-versa with the logic board. There are two sides of the graphics system and you have to make sure that both are functioning properly.

I've seen other codes from other users like -62 and such. If you see 0 as a cause, that means that power was shutoff going to the computer, like someone pulled out the cord. You might want to look at your outlet, UPS/powerstrip, cord and the power supply in the machine. I haven't nailed down what the codes would be for faulty RAM, but I'll leave that up to you all.

Long overdue update. We took our iMac in for repair in May 2015. After keeping the computer long enough to reproduce the fault, they replace the logic board. The iMac worked for for nearly a year.

Last week it started crashing again. We have just a few days left on the three year warranty. I have another Genius bar appointment.

Looking obvious there is a hardware fault. Probably the same components failed on the replacement board.

Hi Guys,

The late update. My iMac has been repaired by the Genius Bar in Miranda Sydney in Australia. Initially, they thought it would be either the logic board or the power supply, therefore they had ordered those parts. However, they have found out that the power supply is faulty and they can reproduce the random shut down during their stress test. They have replaced the new power supply for me. I have been running this Mac for 2 weeks. It is all looking great.

Our iMac is back with Apple. They are going to replace the logic board again.

Fingers crossed it stays fixed this time. The computer goes out of warranty in a few days. If it fails again out of warranty, the repair is £537. Possibly even more since that does not include troubleshooting.

The repair is complete and our iMac is ready for pick up.

In other news my work computer, a Mid 2015 27-inch iMac, is exhibiting the same symptoms. < sigh >

Here we go again!

I had the power supply replaced three months ago and it's still happening. Third apple support call coming up. This is not over!

This will be my second time returning my '27 iMac (2012) to the Apple Store. They first diagnosed the issue saying it was a PSU so they went ahead and replaced. A month later, the issue is recurring.

I only have 20 days left on my warranty, now I'm worried.

I've been getting good results with this technique over the last three months. In December when the shutdowns were happening very frequently and I was using my computer a lot more intensely due to winter break, I started unplugging my computer every night. I've been getting more lazy of late about unplugging the computer and I've even left my computer on for three days. That seemed to trigger a relapse yesterday when it shut down in the middle of a game. It seems to like being powered off as much as possible.

Hi all,

have the exact same symptoms on a late2012 27" iMac with core i7 and the 680MX graphics card which I bought to be safe for some years of innovation. I've not done any reparing other than checking if different RAM configurations are the issue yet and am very sceptical of trying anything after reading through this. Has anything other than being lucky and getting a new Mac worked? It seems to not have, but I just wanted to ask... 😟

Same exact problem here.

Late 2012 27" iMac with NVIDIA GeForce GTX 680MX 2048 MB

Purchased around April, 2013. Random shutdowns started last summer, so a little longer than two years after purchase. I've had it in to the Apple Store just once so far, a week ago. They tried to replicate the issue by letting various animations run in the grapher program for about 36 hours, but no dice.

Their diagnosis was that it was fine and that I should take it home and unplug all my peripherals in an attempt to isolate the issue. Yeah, so did that, and two days later, boom, shutdowns. The first one came after only working on it for less than hour. Happened when I went to open a photoshop doc. Next night, I had two shutdowns within 15 minutes of each other. This time, I only had Chrome and text edit running. Then a third one later that evening.

Going to schedule another appointment soon because this basically renders the machine useless to me. Unfortunately after reading through this thread though, I have a feeling I'll just be out of luck.