iMac (Retina 5K, 27-inch, Late 2015) Randomly Restarts Without Errors

Am I the only one who finds it disheartening that all of us have spend over $2,000 and are dealing with this issue? Wasting our time and energy, being frustrated - looking for a fix for a $2,000 top of the line machine. Wiping the Fusion drive, leaving it for a week for service, sending logs to Apple.

For mercies sake Apple - just replace these Lemons for us. It is the right thing to do.

Take mine and study it all you want. Just give me a new machine.

Your company is worth $640 Billion. It's like me giving my son 2 pennies. Come on.

Not at all. The nature of a software upgrade however is something that can be risky though. I didn't believe it to be so, but things happen. You'd hope they don't, but they do. I have lost my faith in upgrading hardware to new software on any scale. iPhone especially, but now moreso Macs. If things are stable - stay on your current OS. If you desperately need to upgrade, get a new hardware device for it. But that's me, and I won't be upgrading any Mac hardware device for a while given the money I've put into my iMac. iPhone yes, and iPad yes, but only every few years.

By the way, the reason I went with my Reinstallation route (black screen on 5k iMac, not the restarting issues others have) was because I believe I had been migrating from TM backups since Lion or even Snow Leopard and keeping the same user accounts from then. Going a new installation, creating a new user and then just transferring the data itself from the TM backup (taking its sweet time) but seems cleaner and gets rid of any possibility from an older software issue reoccurring due to the previous issue. That's my theory anyway and my iMac has been on for almost 12hours straight without any crashing, so it seems to be working, thank the tech gods.

I totally agree. I now technically have a refurbished Imac I've paid full price for, it annoys me somewhat. Its like buying a new car and getting it with 1000miles on the clock...

Mine has been at apple service center for two weeks.

Will pick it up tomorrow morning , once I've got it home ill see if they 'fixed it' and let you guys know.

As far as I'm aware all they did was reinstall the OS, and since cannot get it to replicate the fault, I asked if they updated it to the latest version to which I didn't get a reply... So I'm not very hopeful at all.

hello! if i were you i'll wait for my free time and send it to apple store rather than wasting time by waiting or searching for a solution! so you can do something else and relax! thank you! it's a hardware issue

Good luck with it all. Hopefully it comes back okay. I went the Internet Recovery Mode route with the support tech and am back using Yosemite (quite enjoy it, as I can change my trash can now back to the Mac Pro 🙂). Steering clear of El Capitan. TBH I didn't see a difference in it at all other than the Mouse wiggle.

Great question. The genius ran the usual diag checks at the bar and found nothing. I insisted that something was clearly wrong and the "tech" in the back agreed to take the machine for a couple of days (I live about 1.5 hours from the Apple Store) and see if they could duplicate the anomaly. Sure enough it rebooted for them. After that I can't really say why they determined it was the logic board. I picked up the refurbished iMac last Sun and haven't had any reboots since. Wish I could help more but I think seeing the reboot did it for them.

Good! The machine rebooted during the diagnostic process for my tech––hopefully he just goes and swaps the logic board, otherwise I might have to do a little back and forth with the techs (not such a loss since, while the Apple Store is 2 hours away, this certified tech lives five minutes away).

And I understand people are frustrated in this thread about getting a "refurbished" Mac––I spent well over $4,000 on my iMac 5k for 4k video editing. And I've used Macs for 20 years. And while this is unusual, it isn't completely unheard of. Sometimes it happens, and yes, while irritating, at this stage I just want to get my machine working again!

It reminds me though not to upgrade my system very often, especially when I'm in the middle of projects!

Just got mine back from shop, it seems pretty stable so far, no restarts , and from their log they had it on for days at a time with no restart. Will keep an eye on it and post if it starts again.

Bluetooth connectivity issues also seem to have been solved.

As far as i am aware they just reinstalled the OS ( which i had done twice prior to sending it in ) ???

I have had the freezing, rebooting problem for a while now. I have had multiple calls with the apple care techs who have tried many different things and were still unable to fix the problem. They restored it to factory settings several times and the problem still existed so they had me take it to the Apple store where they had it for a week and could not recreate the problem. They restored my computer again and told me not to use the automatic Time Machine backup to bring back my data, as they believe it is a software problem. They walked me through manually loading the files I needed Saturday evening, such as photos, music and documents and it seemed to run fine Sunday, but here we are Monday morning 20 June I start working in my photos and the mouse/keyboard freeze up and then the machine reboots. So it looks like it is back to the apple store I go......So frustrating to spend all this money on something I can't rely on. This is my first Apple computer and I wish now that I stayed with HP.

After my first trip to the Apple service place (110 miles away), and having the memory replaced, to no avail, I called Apple again and went back 110 miles and now the logic board is going to be replaced and hopefully I will pick it up this week (another 110 miles each way!). My reading on this board suggests that this is answer so I really hope no one with new logic boards reports any random restarts. I don't know if the Apple service person decided this independently or if my calls and emails to the Apple senior advisor did any good. Stay tuned.

Thankfully my iMac has had no issues since I reinstalled Yosemite via Internet Recovery Mode and decided not to upgrade using a Time Machine backup, but instead to manually transfer my data across (a very long and time consuming process). *My issue was a cut to black at random [when I ran OS X 10.11.5] and not powering on until unplugged for 10+ seconds.

It sounds to me like others are not having success doing what I have done, though they are also not having the same issue as me, theres restarts. I'm hoping you all have AppleCare+ unlike myself (I forgot I didn't have it, until I actually needed it - Murphy's Law) or can fix this with a software fix somehow, not a Logic Board replacement. My Bluetooth Keyboard was stuck last night though, first it's happened ever, and kept pressing keys on the login screen, but a turn off and on got it going again (for the user who had the Bluetooth problem).

Is anyone at Apple reading this thread? It is growing...

These 5K Retinas are lemons. Lemons from Apple. And we all paid over $2,000.

Mine just restarted 2 hours ago.

Did you have a logic board replacement?

I haven't had a replacement, no. But mine wasn't restarting like all others, mine would just cut to black as if someone had turned the power off completely, then not turn on again until I unplugged it. This began with mine as a software issue straight after the minor update to El Capitan of 11.5. I did doubt that I needed a physical replacement for anything. But I also had been using a TM backup since Lion days, so it had all that inherited user data from multiple OSXs. So it was time for a fresh install I thought. Between that and downgrading back to Yosemite, it's worked.

wyowoman, what "Apple senior advisor" did you speak to?

I ask because the Apple authorized tech has performed all the diagnostics tests in the book, and he hasn't found anything wrong hardware wise with the machine. Hence, they can't justify replacing the logic board replacement.

I'm in a rural area that doesn't have an Apple store.

They've been running the iMac with all apps going on 2.5 hours without any restarts. I asked them to leave the machine on overnight and see in the morning if it reports any problems.

Overall I'd love for this issue to go away, but I'm skeptical of picking it up without any conclusions.