Why is my imac shutting down by itself?

Did they mean "Rear housing enclosure"? If so, this would mean the sensors possibly?

I've given up on mine and selling the parts on eBay!

"Rear housing enclosure" is Apple-speak for a set of parts that are usually installed as a group. It includes small cables and sensors. Self-repair is potentially risky, especially if you're unsure of what you're doing. Installation of the rear housing enclosure usually involves some soldering.

I'm not sure what kind of repair we're talking about here. You might want to reconsider your course of action until you/we have more specifics.

Just thought I would throw my two cents in. I have a computer lab with 25 mid 2010 27" iMac's. The majority of which are all blacking out at random. I'm thinking software since it seems unlikely for all of them to have bad hardware.

I have an iMac that is the model of late 2012 27".

I had experiencing this shutting down matter tens of minutesrandomly just about half year before,

But now it had been solved.

After I posted there, and I think it might be the hardware failure or crushes of software(s) initially,
However, the reply and many posts that point to the problem of ram(s).

Then, I installed the memory software (at mac app store) to manage the ram(s), it really works.

My iMac hadn't blacking out and shutting down since then.

Hope it can help 🙂

Which memory software did you install?

Thanks!

Hi Everyone,

I discovered this thread after my iMac 27" (late 2012" began shutting down randomly. No crash report upon re-boot. Applecare advised to reset physical ram upon boot (Command+Option+P+R), and disconnecting the power cord for 15 seconds to reset the SMC. Neither worked. They advised reinstalling OSX. Done, didn't help. IMac is now shutting down randomly 4-5 times PER DAY. It's driving me nuts. I wish I had the freedom of letting AppleCare keep the unit for weeks and troubleshoot it. I'm a busy photographer. Has anyone here found a solution to this?

iMac 27-inch, Late 2012, 3.4Ghz i7, 32GB 1600Mhz DDR3 (factory installed), NVIDIA FeForce GTX 680MX 2048MB, 1Tb Fusion Drive. Running 10.11.2

GordonF238: I had the exact same problem. Sadly, after several (4) trips to the Apple store, they essentially gave up and so did I. It was not under warranty so I was told there was not much else to do. The computer at this point was unusable because it was shutting off 5 to 6 times a day. So, I took it to an apple authorized dealer thinking their technicians may have different ideas. No success there either. I ended up getting the apple authorized dealer to give me a credit for my old computer (my computer was a late model 27 inch), since I decided to buy a new one from them. Unfortunately, the new model has been on order 6 weeks now and I still don't have it. Honestly this has been a total nightmare to deal with. I'm very disappointed with Apple and am surprised at the way they handled this. It just seems very strange. I will probably end up cancelling my order for the new computer (if I can) and going back to Windows since I need a computer. At least with Windows when stuff goes wrong the 'cut your losses and move on' scenario is not as expensive. My advise to you is simply to cut your loses now versus in a few months. You will save yourself time (and money if you factor in your hourly rate) and stress. It is a very frustrating situation I know, but as this thread shows, Apple 27 inch computers have a massive flaw which Apple is not addressing and for which there doesn't seem to be a fix.

Hey CChartersville, and thanks for your reply. Apple sells hundreds of thousands of 27" iMacs each year. I sincerely don't think they're all affected. If anything, I think some of these suffer from either bad power supplies, faulty RAM or SSD chipsets, or have a bad solder joint somewhere which gives way after some time. I personally think the issue is hardware related. The cause could be different for each of us affected, and finding it - as you've said - is like looking for a needle in a haystack. I too am going to cut my losses. I've ordered a new 27" iMac today, and once I transfer all of my software and data onto it, I'll send the faulty one to the AppleStore for troubleshooting, after which I intend to auction it off on eBay (hopefully fixed). It's a bummer, no doubt, but I've switched from Microsoft to Apple in 2005, and was happy to welcome a smoother, more reliable workflow. This does tarnish my perception of the Apple brand, but I'm giving them another shot. Thanks for your message!

I am using the app called Memory Cleaner X, it is a free app in mac app store.

I'm adding my computer to the list, mine started shutting down in late June 2015, In the last two weeks it shuts down 2 to 3 times a day. I can get my computer to shut down every time I try and play a game(Diablo). I don't have applecare so i have been waiting for a solution to this problem so I could take it in and get it fixed. But its looking less and less likely that a solution will be found.

iMac (27-inch, Late 2012)

3.2 GHz Intel Core I-5

8 GB 1600 GHz DDR3

NVIDIA GeForce GTX 680MX 2048 MB

Mine also is iMac (27-inch, Late 2012) version.

I hadn't applecare and still brought to apple for repair, but hopelessly they can't fix it.

Later, I asked in this post, and someone told me that the problem was from the ram(s),

and I had installed the app to fix it. The problem haven't showed now.

You can look up this entire post, you'llcan see that the other possibilities about this issue.

I installed it last night the memory x cleaner, then tried to play bioshock soon as i opened the game up the computer shutdown.

You can look whether it is more than one anti-virus software were installed, perhaps it run a lot of ram.

Or you can try some more utility software to keep the ram clean and made the computer in a good state.

Same problem (iMac 27" Late 2012)

My solution to prevent iMac shutting down is open iTunes and turn on the visualizer, make sure that iTunes not hidden from other windows.

So I have tried every advise that was posted here with the exception of taking imac to Apple because it is no longer under warranty. The last thing that I did was to plug imac to a different outlet in a different room. And guess what? It worked. I had three types of shutdown codes 5 (regular shutdown done by me), code 0 ( related to power) and -128 (which is still unclear). Recently we had a lot of rain in our area and wondring if maybe a moisture is a problem. The room that we use to keep imac does not have crowlspace and seems very damp.

So, if you are still having problems with your imac, give this a try.

I am crossing my fingers that this was a problem. Will probably call an electrician to check on that room.

Good luck!