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

Awesome. Please keep us posted!

Just adding my voice: 27" iMac, late 2012, same intermittent power down issue, repair shop has looked at it twice and can't find anything wrong, passes all diagnostics. It seems to occur more frequently when anything is plugged into a USB port, but that might be coincidental.

Definitely hoping for a recall or a fix!

Thanks for your efforts

Jan-Peter

Update: Took the iMac into the Genius Bar. We weren't able to get the problem to replicate there however they kept the unit for the week and performed a replacement of the logic board. Considering that others in this thread have had the same replacement performed without relief of the symptoms I'm pretty skeptical that the issue is resolved, however I'm trying to be as patient as possible and let Apple figure this one out.

Just out of curiosity has anyone considered a replacement of the video card? That seems to be another constant for all of us thus far in this problem.

Apple has requested that I send them my ailing late 2012 27" iMac, which I have done. Their engineers are going to tear my machine "apart," (in techspeak) to try to isolate the problem/s. Hopefully, they will find the answer. They asked me questions for a half-hour and I reiterated all of the steps I had taken so far, which I had posted here. I had not yet replaced the power supply, logic board or video-card. Mine starting acting up after two years - doesn't this seem to point to some failing hardware? I am more than satisfied with their response and very happy that they are really looking into this.It is just a matter of time now...

So even after having the logic board replaced, the problem resurfaced yesterday. After talking again with Apple we decided to try wiping the computer and booting from an external drive. Once I did that the problem again resurfaced so I have another phone call scheduled for today. The most recent representative that I spoke with was incredibly helpful and has a theory on what may be causing this. Also as an FYI I learned yesterday that the video card is built into the logic board, so a replacement of one usually means a replacement of both. Therefore it seems like that isn't our problem either. I'll keep everyone posted. I definitely urge everyone here to touch base with Apple to verify this is a wide ranging problem with this model.

Good news: Apple has decided to replace my iMac for a 2015 model. I couldn't expect less than that from this great company. I am satisfied with the speed of their response. It will be a couple of weeks or more before I get it, since it's coming from the US to the Caribbean. So far I would like to thanks *****, ******and specially ****** for their due diligence.

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Just a quick update: my computer has not shut itself down for about a month now, since the power unit was replaced. Logic board replacement did not solve the problem either. Still can't tell if problem is gone for good, but one month of really intensive usage without shutdowns looks promising. I even installed Windows 10 just to let my son play Star Wars Battlefront on my downtime, thus giving the GPU a really hard time.

This has to be at least related with the power unit, if not caused by it.

Intriguing - did your rep say what his or her theory is? Personally, FWIW, I suspect insufficient electrical insulation leaving it vulnerable to static electricity shocks, but that's just a wild guess!

I've now sent emails to each of the service members you listed to see if they can offer any insight into this issue. I have another genius bar appointment scheduled for tomorrow so anything I can find out in the meantime would be incredibly helpful.

That's great news! I've had mine back for nearly 3 weeks now after being checked. The problem could not be found during the week it as with my locks Apple dealer and it has not resurfaced since then. I left it on 24/7 for the first week back running Crashplan, backing up my files remotely. It has been used intensively since but at present is behaving itself. However my confidence in this iMac continuing to operate as normal is low, so iI will post back with any updates. Have a good Christmas everyone

I have the same problem, 2012 iMac, 27" i5, 680mx, fusion drive.

I only got this problem after I moved house.

People have said it doesn't replicate when at the genius bar.

maybe poor power quality effects it. Voltage spikes, high line voltage etc.

In australia power is technically 230v but it can be +10/-6% of that legally. So maybe your local distribution quality is effecting the issue?

would also explain why replacing internals also doesn't always fix the problem.

Not saying its not a hardware issue because they should be able to handle anything within supply standard, but it could explain why some people cant replicate it elsewhere.

I thought that, too. Coincidentally I needed to have some electrical work done, so I asked the electrician to test the two outlets I had tried (different circuits). Both outlets fully conform to UK specs, so that should not be an issue.

That's one of the first things I considered when 2 Genius Bar could not duplicate the issue and back home the iMac keep shutting down itself.

But how would we explain that these iMacs work just fine plugged in the same place for a couple of years and suddenly start failing?

It is this inconsistency that makes the identification of the root cause quite difficult in this specific case.

It definitely isn't the outlet with mine as the shutdowns have occurred in multiple locations. Unfortunately none of these locations have been at Apple. The biggest difficulty on my end is that I live an hour and a half away from the nearest Apple Store, so every time I bring it in the problem doesn't surface. Further complicating matters is that the iMac passes all of the diagnostics. For me the issue only occurs when I'm editing in FCPX, and if the iMac has been unplugged for a while, like the drive to the Apple Store, the problem takes a while to resurface. But I still can't understand why when editing the problem always shows up eventually, but when running diagnostics it never surfaces. I think that if my iMac comes back from Apple for a second time without the problem surfacing I'm just going to request to edit on it at the Genius Bar until the problem shows up. I'm really out of options otherwise.

Thanks for this succinct update, I've been reading this entire thread after my late 2012 27" iMac started to turn off over the past 2 weeks.

I've noticed my iMac has a much higher frequency of shut down when playing computer games—and once it has shut itself off there first time into a gaming session, the next shut downs come much quicker. I've started playing games in a window so that I can still see the fan speed and temperature of my computer. Anywhere from 144–163 degrees F has triggered a crash, although 163 seems to be the peak of heat at any given time while playing and the game can run at the temperature for a whole match without the shut down.

After crashing during a game, my computer is more likely to crash doing something much more mundane, like opening Maps. But for the most part, I can be streaming from the internet for hours on end with no intermittent shut downs. It seems the "bout of shutdowns" is always started with a period of more intensive usage, like gaming.