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

All I can tell you is what helped me and solved it until today.

I uninstalled Anti Virus Software and Steam. In my case it was Safari which was the problem. When I switched to Firefox I had no problem at all.

On my side it was a Software issue but it seems there are lots of causes for this behavior.

Hi there! Just a little update that works by the moment for me.

My shutdown problems started on June, I live in Barcelona so in June is very hot indeed. My office is on a attic where is so warm. I suspected that the shutdown problems where from that but I've installed Mac Fans Control and I thought that will solve my problem.

After few days trying some methods (installing a clean SO in another partition, replacing RAM modules and so on) I moved my computer to the bottom flat in my office. The temperature was fall (in the near processor sensor) from 51/58º to 42/44º... Since 2 days here with the iMac running a lot of applications the problem seems to be solved.

I hope it helps someone.

Just an update. After being promised that Apple was going to replace the iMac, three weeks later, still have not received the product.

Just an update from me - after updating the OS its getting better. My Safari Bookmarks are not mixed anymore, this is solved. But from time to time I still have that shutdowns... I will wait until sierra is out (no beta) and hope that will solve it once and for all...

Oddly, I've noticed that occasionally (perhaps one in every 10 or so events), I am able to press the power button and the machine will wake from hibernate. I'll get the series of dark grey rectangles across the screen that sequentially lighten and the machine will restore to its previous state.

Why (or how) an iMac is going into hibernation, I have no idea. I always count it as a win if I can recover from a hibernate. unfortunately it does mean I'll be due another event somewhat soon.

Hi guys,

well I'm back & the problem has resurfaced after 5months since the following parts were replaced: logic board, power supply and power cable.

Spoke to Apple about it & they have suggested I take it back in (again) to get it checked. I can't believe this is still happening after all this time. It's 9months now since the shutdowns first started & I don't believe it will ever get sorted

I've been an Apple customer for 25yrs and I'm feeling a bit let down :-(

I'll keep you posted.

Hey everyone,

My iMac 27" never got fixed. The problems persisted even after replacing the logic board, memory, power supply, graphics card, etc.

Apple decided to replace it with a brand new 5K iMac. I think you guys should continue to talk to Apple and keep the conversation going. Obviously, don't be an *** to the person you're working with. Apple continues to have one of the best customer service so be respectful, courteous, but at the same time, address your concerns and explore all possibilities to solve it.

Another one to add to the list, Late 2012 27" i7 iMac. So far I've had the 3Tb fusion HD replaced, logic board replaced, power supply replaced, airport card replaced, RAM replaced.

And the random shutdowns continue, 4 already before lunch today needing an SMC reset.

It's going to the Apple store yet again on Friday, let's see what parts they throw at it this time. They claim the problem has never happened when the machine has been in their hands but I've shown them video of it happening and kept console logs.

I'm actually quite surprised it's stayed on long enough to type this.

Hi - I am inclined to agree with you. Having not had the problem for about 2 years of constant use the machine shut down yesterday which was the hottest day in our locality for quite a long time. Not a solution but it could indicate a cause.

Looks like all the problems are being caused by processors with 77 watt TDP (Thermal Design Power)

I suggest that the 3.2 Ghz i5 folks ask for an upgrade to the i7 3770S processor,

which is 65 watts.

The i7 3.4 Ghz folks can put a 3770S in, but it's a 3.1 Ghz processor.

A small fan may help, I use a USB fan when doing processor heavy tasks

Hello guys, for those who think that is a temperature problem. I've find a very good software to monitor and log the temperature of all your sensors. https://www.tunabellysoftware.com/tgupdate/

(You need to purchase the Mac Store version to run with all the features - Cost 12€)

Maybe we can share the temperature data when a shutdown occurs.

Today was a very hot day in Barcelona, 3 shutdowns in less than an hour. I've reduced the temperature of the room and no more shutdowns by the moment.

I'll keep you updated. Good luck!

Good plan ......will do the same and post results.

My favorite fan control program...

http://www.crystalidea.com/macs-fan-control

A new shutdown today. I left my iMac working with iTunes and XCode for a minutes and... ¡boom!

Thanks to TG Pro I saw the temperature log. My normal CPU core temp was between 42 and 52 Cº, at the moment of the shutdown up to 63 Cº and keep at this for a while after the reboot.

I'll try to buy a couple of USB Fans to try to freeze a bit more. Any suggestion about other fan or cooler system for the iMac?

hi to all, the shutdowns seem to disappear if i set monitor and hard disk sleeping mode to 3 hours (preferences/energy saving).
could you try this setup and report if your shutdowns will stop?

thanks.