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

I dont think that all of the related issues in this post comes down to just one issue.

My temps are not to high, 65-70 in normal use.

Today I had another random shutdown by simple opening Safari. I clicked on the Sarafi Icon and the screen went black and the system was down. I had to wait 10mins before I was able to restart it.

I do have the i5 3,2 - that would fit in the profile but I also had 95 degree within games without problems. It always occurs when Safari is in use. When I switch to Firefox everything is fine. I just dont like Firefox on my Mac...

I think this is a Software- and Hardware Problem.

Just my 2 cents.

Hello Mission Complete,

So have you experienced and shutdowns since you had the power supply replaced?

why it shutdown when you try to reset pram?

i don't know if it could be only a software problem....

anyone has tryed to install maverick?

I have this problem from some update ago of el capitan....

I just go the random shut down happen again on my 2012 iMac 27inch, since the apple shop replaced the Power Supply 6 months ago. It shutdown 3 times last night. I am very disappointed with this product. Apple should provide replacement program for that.

Done some further testing using the Apple Service Diagnostics, ASD OS and ASD EFI from a bootable HDD whilst waiting on delivery of a replacement power supply.

I started the tests using the ASD OS and within two hours the iMac shutdown. Repeated the ASD OS test and the iMac shutdown again . During each successful loop ( before shutdown ) of the ASD OS test no faults where found and test reported as a pass.

So after this I ran the ASD EFI test for over 16 hours ( no faults found ) and the iMac did not shutdown. Straight after the ASD EFI test I then ran the ASD OS test and within the first 30 seconds of the test the iMac shutdown, I restarted the iMac and again the ran the ASD OS test and it shutdown again within 30 seconds, tried again and same happened.

After this, the iMac was booted into OS X El Capitan in safe mode and no shutdown observed as yet.

I'm now wondering:

Could this possibly be the power management difference between ASD OS and ASD EFI diagnostic testing hence the sudden shutdowns when using ASD OS ?

Having now replaced the power supply, I ran the ASD OS test. During the last test where the iMac shutdown was during the WiFi / Bluetooth sleep, wake and standby tests. On this occasion the ASD OS now reports that this has failed.

It seems that the problem has roots with a faulty power supply and WIFI/Bluetooth module. Especially wake, sleep as the power will be directly related with this.

Intresting, folk have commented that the shutdown happens when using safari. So from here my next plan of action is to remove the Wifi / Bluetooth module and test to see if the intermittent shutdown persists.

The old PSU

I ran a 4 hour ASD OS test this time, but unchecked Bluetooth, Airport. No intermittent shutdown during tests. The test ends successfully. I then decided to perform a PRAM reset to test the Bluetooth and Airport, this time the only error reported is the Wake on Wireless Internal Simulation Standby Test.

I'm more convinced that the power supply is has been the problem. The Wake on Wireless Simulation test is most likely software / firmware.

If I experience another intermittent shutdown on my iMac i will update it on this post.

One more client in the list:

iMac (27', late 2012) OSX Yosemite 10.10.5

1 To fusion drive

3,4 GHz Intel Core i7

8 Go 1600 MHz DDR3

NVIDIA GeForce GTX 680MX 2048 Mo8 Go 1600 MHz DDR

- the original Hard Disc has been changed after a total crash (apple-care 1st year)

- the screen has also been changed (de-coloration in the lower corners and 20 insects, or black spots here and there, apple-care 3rd year)

Right after the screen has been changed the problem of sudden shut downs started to appear... at first I didn't realise what was happening. I rarely turn off the computer, I rather put it to sleep or put the screen to sleep, so the computer can keep on working while I do the sleeping, but I remember sometimes finding the computer turned off in the morning. I was thinking maybe the electricity being cut off (happens often here in the countryside when there is a lot of windstorms) or that somebody else in the family turned off the computer...

It took some while to identify this problem, but one day it happened when I was in front of the screen... and then it started to happen more often... two or three times a day.... by this time, unfortunately my Apple-Care has run out.

I called them anyway, and they tried to do some things but nothing worked out (cleaning out all the preference files, starting in safe mode etc.)

One strange thing I have noticed is: when trying to reset the P-Ram the computer shuts down "black out" after the first "gong" without finishing the procedure and then the only solution to restart the computer is to unplug the electrical cord for 5 minutes... "SMC reset"

Console : kernel[0]: Previous shutdown cause: 0

Unplugging the computer over night is really helping to keep the computer working the rest of the day, but this is not a solution in the long run.

I have to bring in the iMac to a service-center for observation and report. (at my charge)

I will report here the solution they hopefully find.

OK I am another one to the list with one of those shutdowns 😟

iMac (27', late 2012) OSX El Capitan 10.11.6

3 TB fusion drive

3,4 GHz Intel Core i7

32 GB 1600 MHz DDR3

NVIDIA GeForce GTX 680MX 2GB

What I tried so far is to install the original RAM the iMac came with (8 GB), but with no change regarding the shutdowns. Next stept would be to change the power supply but what I read here so far I have only little hope that will change anything... 😟

Has anybody tried to change the SSD card on the motherboard that is part of the fusion drive yet ? I have read some have changed the HDD already what does not seem to help but I haven't read that anybody has changed the SSD card yet.

I replaced my power supply and have not had any problems after running a 24 hour Apple Service Diagnostics test. Highly unlikely that your fusion drive SSD & HDD are causing problem. Try connecting an external hard drive to your iMac and install OSX El Capitan on that external drive. Then boot OS X from the external HDD and confirm if you have intermittent shutdown when using OS X from external drive.

Ah OK good to know. I will try changing the power supply then...

It started with Safari Problems. Whenever I surfed the web with Safari, I got these shutdowns.

Then I switched to firefox which solved it for some weeks but now its coming back.

I got this solved again (don't now for how long) witch setting the fan to max rpm. Its louder, of course but since then not a single shutdown anymore. That brings me back to temp. problems which are maybe the cause. I will let you know when the shutdowns return. So far so good.

Nick,

Don't think temp is the cause, most likely your power supply unit is not powering yourAirport ( WIFI ) Card properly. I also noticed during my diagnostic testing that my Airport Card failed wake and sleep tests, those wake and sleep tests are a good indication something is wrong with power.

When I replaced my power supply unit my iMac passed tests on the Airport Card.

If temp was the main cause, then the shutdowns would be predictable. These iMacs have plent of sensors, on reaching a specific temp then your iMac would always shutdown, that's not the case here. The shutdown cause error 0 ( sudden loss of power ) logged also points to the PSU.

Glasguy,

understood.

But as I read so far in this thread there are some people who changed their PSU and after some time the shutdowns happened again. You mean this problem comes back from time to time or is there a bad amount of iMac models with the "wrong" or not working PSU? As I read, this also affects 5k iMacs, so this is a problem of more then one model?

I agree with you, if temp would be the main cause you could force shutdowns only by high temp. Thats def. not the cause. But it may affect the problem here - lower temp may let the PSU work in more stable parameters.

I just down know honestly what to do, I just can try things out and when it works, we all can be happy. Its so nerve wracking with that shutdowns...

Nick,

I seems that 27" iMac 2012 up to Retina have reported problems with intermittent shutdown. The 27" iMac service manual is the same for 2012 /2013/ late retina 2014. I'm wondering if Apple use's more than one manufacturer to supply PSU's for these iMacs, also wondering if they use refurbished PSU's for replacements. My faulty PSU is made by delta Electronics, my replacement is made by LiteOn. That makes sense what you mention that low temps may let the PSU work in more stable parameter. It a spoiler having uncertainty and no confidence when using the machine.