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

I can't speak for Robert, but after four trips to the Apple Store, one futile logic board replacement, two futile hard drive wipes and finally a power supply replacement, the iMac hasn't shut down on me. I'm still slowly ramping up the work I do on it, but at least it's not instantaneously shutting down as it had before. I'm still horrified that even though it hasn't shut down yet that the defect is still present and just working its way through amother power supply.

I'll keep everyone posted but thus far the power supply replacements have had the best immediate results. Furthermore I've informed every Apple rep of this thread though none have taken much interest in it. I'd advise you all to do the same.

Thanks everybody for keeping us posted.

So the bad capacitor theory is gathering some steam, and this is comforting somehow.

Apple are you there??? Can someone give us some support on this?

Similar problem except the shutdown happened only once and the iMac never recovered. Had to change the logic board which is costing me $500+. How can I trust Apple after this? This machine has Apple's HW and Apple's SW. So why the heck should I have to pay for their faulty build? This *****!

The whole premise of Apple products being expensive and non-repairable is based on controlling the HW and SW, to provide a great user experience. So when it fails, Apple has to OWN the full responsibility and replace the system - no questions asked.

Krishna

Same problem, same make, model and year. Had it to Apple three times. Like others, they were unable to replicate even after keeping the unit the third time for a week. I told them to look at these threads so they'd acknowledge it is not an isolated incident. In their infinite wisdom the Genius Bar started to blame my home office setup and wanted me hire an outside consultant to review it. As if I or any of us need someone to look at how we plug in our Macs! It was actually quite insulting. I've checked the power at the moment of shutdow at both ends and there is no and never was an interruption. Funny thing, after the third visit the problem vanished for a few months but now shows up nearly on a daily basis. This makes one wonder if the simple act of physically moving the machine causes something to happen to temporarily resolve the issue. This could explain partially why so many of us have taken out units in with Apple unable to replicate the problem. Seriously does anyone know a good class action attorney? Apple avoids any comments here or any official acknowledgment as they certainly realize this could lead to a costly recall and bad PR, God forbid! I'm checking with the FTC. Something needs to be done to make this right for us!

One of the things we seem to have discovered on this thread, and that allowed me to finish a project on the iMac before taking it in for repairs, is that if you unplug it for an extended time, say overnight, it usually stretches the amount of time that the iMac will run before the problem resurfaces. I think this could be the issue you dealt with. It also seems common that this fix only works for a while and the interval time before shutting down reduces over time.

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 >