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

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.

It's weird but I've tried. I'll let you know 😉

Hi! I've tried but the shutdown occurs again 😟 Good news! I think I found how to reproduce the problem!

Hi everyone! Good News! I think I found a way to reproduce the shutdowns! This is fantastic because if we can reproduce it we can solve the problem! 🙂

Following the theory of CPU overheating (or other component overheating) I make the following steps to force a shutdown:

• Install any fan software to see what's your CPU normal temperature (I'm now between 42-52 Cº in my CPU core 1 sensor).
• If your software allows to you to increase the fan speed. Disable this option, we want to force a overheat so make your fan as slow as you can 👿
• Open as many programs as you can (And see how the temperature is growing).
• Finally, open any 3D game to force a little more the CPU.

See how your CPU temperature is growing, when the CPU exceeds 65º then you will have your shutdown.

Please guys, could you try to reproduce this steps and take note of the highest temperature of your processor?

I hope this time we've captured that awful gremlin.

Another way to reproduce the problem for me is trying to reset NVRAM. When I try it (using the Command (⌘), Option, P, and R. when chimes) it shutdown and don't start again at least after 15 minutes...

How to Reset NVRAM on your Mac - Apple Support

Could you guys reset your NVRAM without problems?

It's true. This is compatible with software problem for me....

But why it doesn't appear in log file?