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

Thanks for that info - then it makes sense that all iMacs beginning from 2012 having these problems.

Just 10mins ago I exchanged my 1TB Harddrive with a 1TB SSD. With this I saw A LOT of dust in the iMac as it was mentioned above by other users. I tried to clean it up as good as I can. It really were flakes of dust and compressed dust. The fan was free, not jammed or something but of course also full of dust. Hopefully its now getting better. I also set fan speed back to default. The OS is controlling it now, we will see if strange behavior will occur. I'll drop a line if so.

Nick,

Can you confirm what brand your power supply is, does it look healthy when the dust is removed. Do you have white ingress marks on the PSU.

Glasguy,

sorry but I just put in a new hard dive, I did not dismount the logic board the install it. Therefore I did not see any labeling of the PSU.

I did it.

But shutdowns persists

I simply cannot imagine that Apple does not know what the core of the problems is. They are so much in control of their products and the assembly of them, our problems must be known.

I would not mind spending money on fixing my Mac, but I don't want to end up replacing part after part - and wasting lots of money - until the Mac is fixed.

Apply should be able to point out that if you have PSU model xxx or CPU model yyy etc, then you should do zzz.

Please, our son was just doing his homework on the Mac today and suddenly the Mac turned off. And since he did not know that he had to unplug the power for 1 Minute, he never got the computer turned on again.

And he was furious that some parts of his assignment was lost, which I understand.

Well, I presume everybody has seen this notice. iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program - Apple Support. Clearly Apple recognize the problem with our build, models but only those fitted with the AMD Radeon HD 6970M video cards . All of our models are based on the NVidia Card. When will Apple address this ?.

Sadly does not apply. Suffering with a NVIDIA GeForce GTX 660M.

OK, so I have had my late 2012 27 inch Imac back from apple for exactly one week now after taking it back to them a second time with random shutdowns. The first time was July 14th and they replaced the hard drive which did not solve the problem. The second time, they kept if for a week and ran every diagnostic test they could. Of course, the computer never shut down. They did not replace anything BUT, they did give me a brand new power cord. I plugged it in last Saturday after I got home and I did not not shut it down until last night. Now, I am not saying that the power cord solved the problem; I am not saying maybe the computer kind of fixed itself with all the test Apple did on it; all I am saying is that for one entire week, my computer has not shutdown, and it has been acting and running like I just bought it. It is so fast and snappy, and it acts like it is supposed to. When I turned it on this morning, it powered up in seconds and I have had no issues waking it up, no shutdowns, and no sudden loss of power kernel. I am afraid to say anymore because as we all know, this shutdown thingy can occur at any time. However, so far, fingers crossed, the new power cord SEEMS to have solved the issue. I will definitely be back to report if the shut downs return. I just wanted to maybe help someone else that is having the same issue, maybe a new power cord might be the answer.

The iMac has a standard power connector so a normal power cable should fit. Have some laying around here so it is worth a try.

Unfortunately this did not do the trick for me :-(

stjohns,

Hopefully a power cable may have resolved the intermittent power fault you experienced with your iMac.

I'm assuming your iMac is covered by Apple Warranty. To be certain that your problem is resolved, try running some prolonged tests on your iMac for upto 12 hours to slightly stress the iMac. Having run Apple Diagnostics I can confirm that my Machine would pass the Apple Service Diagnostics ( ASD EFI ) after 24hours running, but would fail the ASD OS based diagnostic testing.

Try, see if your iMac shutdown when running multiple applications.

If you can, multitask the following applications and let them run for up-to 12 hours:

Unigine Valley ( not full screen )

https://unigine.com/products/benchmarks/valley/

And

Play in Safari and Chrome ( mute volume )

https://www.youtube.com/watch?v=SkgTxQm9DWM

And

Play iTunes Music

And

Run a VM Machine ( install Windows or Linux )

https://www.virtualbox.org/

If shutdown, then go back to Apple whilst you still have warranty.

Hi all,

Same here my late 2012 27" iMac turns off randomly, sometime 10 times in a day sometimes keeps going for days.

I've tried the following.

- Swapping memory

- Clean install

- Changed Hdd to SSD

- Did hardware scan at boot ( no errors)

- Changed power cable

Also i need to pull plug out for 5-10 minutes before i can turn it back on, and it actually turns itself on as soon as i plug it back in. ( no need to press the power button) I don't if that may incline towards a faulty power supply.

Please let me know if any of you were successful in troubleshooting this!!

Thanks

Hello everybody. Now I join to this group of Late iMac 2012 with those problems. I had an 27 inch iMac late 2012 i5. Its the same as most of you. Shut down randomly, and it takes a long time to start up. I have to put out of the electricity for 10 minutes or more. I brought it to the apple store and they didn't find anything and couldn't reproduce the problem. I don't know what could be, but I am waiting a solution desesperatly. What would you recommend? chang the power cable? all the power supply? If i disconnect from the electricity for a day the problem don't appear in a long time.

Since I shut down my iMac late 2012 i5 whenever I left it, I don't have this shutdowns anymore.

I had these shutdowns when I just send it to sleep or it runs the whole day in idle mode.

I would recommend to shut down the Mac during night if you don't do this already. IMHO the power cable shouldnt be the root cause. I exchanged my 1Tb HDD with a 1TB SSD and since then I had no shutdowns but since this hard drive change I shut down my iMac during night and when I left home during day as well.

This problem is so various that I don't think we can solve this for everybody. Maybe it really is all down to the Power Unit. I will install a m2.sata SSD within the next weeks so I will check which PSU is installed in my mac but this really could the cause for us all. Also the theory of the CPU frequencies could be responsible. Maybe a CPU chance to low power or any other type of what you now have installed could solve it.

I just think its down to electricity - if the Mac runs a long time without restart it may reappear but I don't wanna find that out...

I fully agree with NickFromLE, if changing the power cable does not work (thats the cheap option), the most obvious elements are the PSU and CPU.

I wonder of the people who earlier had their PSU replaced and still had the issues actually just got the same model/variant installed. That would not surprise me.

Again, I would not mind spending money on changing the PSU if I knew it would solve the issue(s).