iMac 5k powering off by itself

I just read another thread in which someone had their display replaced. The sensor was overheating and the only way to replace the sensor is to replace the display. Pricey fix but that's what fixed it for him. It was a hardware issue, not software. Here's the link.

https://discussions.apple.com/thread/7392013?answerId=31261071022#31261071022

Wondering if anyone has had any luck getting to the bottom of this issue.

As with most above, mid 2015 retina iMac - kept it current on updates - for the past few months started powering off in the middle of work. As of now, I get about an hour or two of use before the machine shuts off - and once it does, it's an hour or less for the rest of the night.

Same details - have to unplug the iMac, or cut power to the UPS. In my case, I have a UPS with nothing else plugged into it - just the iMac.

Brought it into the Apple Store, and after leaving with them for a day I received a call from a helpful person who found nothing. Brought the iMac home, same problem returned the next day. Brought it back, and this time received a call from an incredibly unhelpful person who told me there was nothing wrong and no recommended course of action (because there's nothing wrong), so if I want to get parts to replace it, I could expect to pay 1700 - 2200 dollars (that's not a typo - I would re-buy the iMac if I went this route).

I finally spoke to someone else, who agreed to roll the machine back to El Capitain, which they did, and there's been no change in the behavior - still powering down.

I've been building my own PCs for decades (network / SAN administrator here) and in another room I have a PC I built in 2012 that's still humming along, and I've absolutely punished that machine. The iMac, on the other hand, sits on a desk being babied, is largely used for scrivener and web browsing, and won't remain on for a night's worth of work. Without a resolution, I don't see how I can seriously consider buying another apple desktop if it's both going to break in 18 months AND remain unfixable according to the store technicians. I would pay for a new logic board in a heartbeat, but from the replies above, that's not going to fix the issue.

Anyone have any better luck than I did?

Btw, I am having the same issue w my 5k late 2014. Am taking it into the Apple Store today and am going to show them the thread on the display replacement. I'm super annoyed that this is a problem for so many people and nothing has been done to resolve it. I'm surprised there hasn't been a class action against Apple at this point. Customers spend thousands of dollars on their products and to have something shut down then be told there isn't an explanation as to why by the manufacturer is inexcusable. A fix should be found immediately.

This is not common to Apple products by Hard disk itself. Probably your external disk brakes inside contents through USB dock.

Procedure: Extend AppleCare first, then contact Apple Customer Services on (800)275-2273

I would take the iMac into the Apple store for diagnosis. I would also purchase AppleCare and register it as soon as possible.

My mid 2015 retina iMac recently started doing the exact same thing ! Did you ever figure out what was wrong ?

Mid 2015 5k iMac

32GB RAM

OS 10.11.6

Yesterday it went into a "coma." Today it started increasing frequency. The screen will go black, the power button becomes unresponsive. I unplug for 10 seconds and re-plug and it will boot up. Reset PRAM, ran diagnostics (all good), still had the issue. Did a new OS X install and restored rest with Time Machine. Issue persists.

I believe you may have the same issue as I have. This was caused by upgrading to OSX 10.11.4.

The iMac shuts off at random and needs to be unplugged. This only started occurring for me the day of that minor update. So far I've downgraded to Yosemite, had my Logic Board replaced, and it has still persisted. Other people have had a similar issue with the OSX minor update, but theirs restarts only after pausing. Mine just cuts to black during very simple tasks - opening Safari, opening Preview with new images - but also even whilst idle and only a Time Machine backup is occurring. (last night whilst I was trying to backup my machine again before sending it in).

So far I've searched everywhere and no one can find a fix. It was caused by a software update, but that doesn't mean it's only limited to the software being an issue. Others having the pause-restart issue had their Logic Boards replaced and it fixed theirs. Not so lucky for issue though. I'm taking mine back to our local repairer and telling them to take as long as they want. Not really any use to me until it's perfect again, like it was prior to a minor update.

The Senior Apple Technician quoted it best when he said 'an upgrade is like doing open heart surgery on your computer'. It definitely is true for this case. Never upgrading again.

I have the same iMac and it's happening the same problem. Did you solved this??

I haven't verified yet, but I think it may be the Power Supply Unit. I'm waiting to take it into Apple when I have the spare cash, since it's beyond warranty and I don't have Apple Care.

Hello,

I was wondering if you've found a solution for your mac, as I've got the same machine with the same issue, replaced Logic Board already ( it's been in repair for 2 weeks) and it's happening again after a week.

Thanks

I added a small uninterruptible power supply to ensure a steady, clean flow of power. Since then, in two weeks, I had the issue once during a reboot/login. Previously, my iMac was shutting down with increasing frequency, usually after I logged in. Turns out, there was a PC laptop power supply on the same power strip that went bad and when I replaced it, my iMac issues slowed quite notably. My conclusion is that the power supply unit is sensitive to electrical current fluctuations and if you have a power strip or circuit running a lot of devices, the variable current forces the iMac to protect itself.