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

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).

Hi Beolion,

I have a late 2012 imac, I can replaced the PSU from apple store due to the random shutdown issue. The computer was working ok, but the random shutdown happens again 6 months later. I am pretty sure Apple just replaced the Original PSU unit rather than getting an upgrade to resolve the problem.

When I reboot in 'safe mode" the problem seems to go away. Any things on this and how to pin point the cause?

thanks,

hank

Hi hank,

well thats the other side.

When it first started (the random shutdowns) it turned out to be Safari. Whenever I used Safari, I had this shutdowns.

Then I switched to Firefox and the shutdowns went away, not a single one for weeks but then it startet also when I changed the volume of the speakers or open the AppStore.

Since then I also think of a Software Issue - so maybe its the PSU, maybe the CPU but also maybe the Software...

Experiencing exactly same issue here... iMac 27 (late 2012) with 3.4Ghz i7, 32gb ram. The quirky thing I have found that there are no issue when I boot in the 'safe mode'.

This leads me to think that it is a software issue. I'm still working on it, do have replacement RAM coming from Crucial and call with Apple in the am.

Has anyone else had the same experience with safe mode?

Hank

I have a similar machine. Late 2012 i7 3.4GHz 32GB 680MX. I got my power supply replaced by Apple Store itself in Istanbul around 10 days ago. I never tried to replicate the shutdown problem in safe mode but I even got the shutdowns on the windows 10 partition and another partition that I created for testing purposes.

Apple Store itself of course couldn't replicate the problem like almost everyone else in here experienced. It's probably down to power supply not being powered on for far too long). But they still replaced the power supply for around 115 US Dollar (340 Turkish Liras)

By the way as far as I'm told it's a 300Watt part. While I was at it I asked them to fit the machine with some other type of power supply made for other, possibly newer iMacs that utilize a higher wattage part. They refused to do so. Apple policies obviously. I haven't asked about the brands of the outgoing and incoming power supplies. I'd do so if I had read the related posts in here.

Long story short, for the past ten days the machine has always been on, I had played Civ V for like 10 hours at once, max. settings and so far no shutdowns. So, tho Apple Geniuses failed to replicate the problem and tho it seems like a problem Apple itself should acknowledge and pay for, apparently the replacement of the PSU resolved the issue.

I just removed the 32 G of Ram for return to Crucial, and inserted the original 8 and now its working fine (so far)! Maybe the power supply has trouble with 32 g?

Imac needs Ram to be 1.35v, maybe your 32 gb were 1.5v. Might be what was making the PSU turn off

Thanks ngrant, good thought, but the spec is 1.35v from Crucial. Can the power draw go up with age?

HERE IS THE FINAL DEFINITIVE SOLUTION FOR THE PROBLEM!!!!

We have only one solution:

Apple have to replace the power supply unit with a reinforced/modified one

to all the owner have random shutdown.

They replace the PSU and for a variable range of time, users does'nt have the problem.

But the PSU is the same of the original one with the same problem...

Every one of us of this topic have to send a message to

Apple here:

http://www.apple.com/feedback/

This is a preferred way to comunicate with Apple Support.

this is a special channel that Apple consider with particular care.

at the end of the mail copy the link of this thread: https://discussions.apple.com/thread/6176570

so they can read that we are a lot of dissatisfied users.

I do agree with ElBartolomeo. I have just submitted the feedback form to apple as the bug report.

I hope all of us can follow ElBartolomeo 's suggestion and raise this issue. Obviously, this is a faulty PSU.

I can't even sell this iMac due to this issue.

Hopefully, Apple will provide the action and solution to fix the problem.