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

Those temperatures look a little funky to me.

Looks like they say Celsius, but are actually Fahrenheit...

100 Cº is 212 Fº, the temp where water boils....

I still say this is a power problem with the 95 watt processors, and overheating...

Jack up your CPU fan speed and see what you get.

My 21 inch I5 running at 2.5 is at 90 Fº, and I have noticed it gets to 110 - 120º, unless I override the fans, which I have done...

Also look for stray processes eating CPU cycles up....

before the shutdown my imac's fan don't go up with rpm

when the problem didn't exist i could play with heavy games and when cpu temp grow up, also the fan speed up the rpm...

now the shutdown sudden came without previous speedup of the temp....

probably temp is not the problem...

That is a new theory, and quite interesting, especially if this is the cause. Why make you believe that the problem is related to the 77 watt TDP? What CPU models are 77 watt TDP?

My CPU is Core i5 (3470), but the problem is that a CPU change is quite difficult and relatively costly.

Would certainly be helpful if we could get any statements from Apple soon.

Look at the processors offered for Late 2012 iMac,

https://en.wikipedia.org/wiki/IMac_(Intel-based)#Unibody_iMac

Intel i5

2.7, i5-3335S (low power, 65 watt)

2.9, i5-3470S (low power, 65 watt)

3.2, i5-3470 (77 watt)

i7

3.1 3770S (low power, 65 watt)

3.4 3770 (77 watt)

The vast majority of people having problems are using either the 3.2 i5 or the 3.4 i7, both 77 watt, and have a 27 inch screen.

Looks like retail for a used i7 3770S or 3770T (45 watt) is $200,

http://www.reusetek.com/intel-core-i7-3770s-sr0pn-3-1ghz-5gt-s-lga-1155-processo r/

Knock, Knock, Apple...

Knock Knock...

Major problem found here.....

You need to adjust the temp sensors responsiveness....

CPU's need to be cooler....

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.