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

Apple is trying to cover this defect up. I sent my Supervisor a listing of a bunch of 5K (late 2015) 27" models that Best Buy is reselling for half the price I paid for mine! Bought mine at Best Buy on sale. Not happy.

He also said under no circumstances would Apple send me out a NEW replacement computer in exchange for mine. So much for Apple's stellar customer service mantra. The company just doesn't care.

It seems we are all stuck with these Lemons...

Happening to mine also, except it isnt restarting at all. It's just plainly going straight to black. Pressing the power switch does not turn it on again either. I physically have to unplug the iMac before the power button works. This is ridiculous. Updated to the very latest minor software patch yesterday. It wasn't happening prior to then.

Just an update - just got my 27 inch iMac back from the Apple Store Genius Bar. They replaced the entire Logic Board and told me the error was with a defective video card. Just about 45 minutes in, and no problems yet. I also got mine at Best Buy... on sale... late 2015; noticing a trend here.

Onward; my advice is to get this to the Genius Bar stat - they'll fix everything for free.

I passed your post onto the Apple Supervisor I am dealing with and requested a Logic Board replacement - he is waiting to talk it over with the engineers. But it sounds like you have found the fix. Today it did a funky restart with just a black screen, then the El Capitian background and no icons. Had to physically shut it down with the power button. These restarts are a real pain and this last one was troubling. Glad to hear yours seems stable.

Hello,

Just an update to my issue...Apple Store called back...found no errors on all test, however on booting up errors, so logic board replacement.

Will update on more news. Just a note on this. I have the iMac 5K Late 2015 entry iMac with AMD 380 2GB. Do any of you have different models.

If this is happening on all models from that line of iMacs there should be a recall notice !!!!

-bl

Mine is the top pre-configured model with 2 TB Fusion Drive.

-KJ

Mine is a late 2015, Retina 5K iMac with AMD Radeon R9 M390.

I have heard the downgrade does not work - once upgraded the bug appears and doesn't go away.

I am all for a recall of the late 2015 - 5K Retina AMD Radeon M390 - that is my model also.

But Apple doesn't care about it's consumers one bit, they are one of the big guys now and making money over customer service is their game plan. Hence their stock price is dropping. I will never buy another Apple product again - my 8 year old also hates Apple now as the computer crashed while he was working on a project. Way to go Apple,

I feel really good about my $2,000 investment into your company. Now step up to plate. The engineers have been looking at my logs for 45 days and no resolution, Just send me out a RMA - and send me a new unit. Simple. Make us happy and loyal.

They don't even read these threads - I sent it to the Supervisor I am working with and I don't see any post by Apple.

I was almost tempted to drop $800 on a a PC so that I could have a working machine, but then I would be out $2,800...

Awesome! Thought I'd throw my voice into this discussion.

Same deal. iMac 5k late 2015. Went from 10.11.3 to 10.11.5––bricked the machine and started having these freezes/restarts every 10-20 minutes. Console reported Error -128.

Used Time Machine to go back to 10.11.3––problems persisted.

Erased the drive in recovery mode, and re-installed to 10.11.5––problems began ten minutes after install.

Now it has been dropped off with an Apple approved tech––hopefully they conclude it is a hardware issue, because their initial diagnostics revealed nothing wrong (and we all know that's not true).

I'll have an idea Monday/Tuesday if the logic board gets replaced similar to Michael M's iMac.

FTR, quick update. I have successfully migrated all my "stuff" from Time Capsule. Now on day 5.5 and still no reboots. Yay.

(Mine was the one the logic board was replaced.)

Hi Michael M, when the techs checked out your computer, how did they conclude it was a Logic Board problem? The apple authorized tech did the first, standard diagnostics test and found "nothing wrong" with my computer.

After speaking with Apple Support I attempted to go the way of wiping my FusionDrive (which took a while due to complications) via Internet Recovery Mode, and eventually restored the 5k iMac back to Yosemite. It was late at night and it had been on for about 5 hours (in recovery mode all those times) but once Yosemite was installed, went straight to black during the setup process of adding a new user. At that point I went to bed.

(My issue was not the iMac restarting at random [like most people here] but that it would shut off to a black screen at random, as if the power had been turned off, and wouldn't power up until it was physically unplugged for 10secs).

Anyhow, woke up this morning, no issues setting up the 2 new profiles, and currently getting data from a TM backup. So far so good with no issues with shutting down at random (so far!). I can't fully say it's fixed, but I'll attempt to slowly rebuild my data to it, and keep it on during the day and see if it happens again. So far it's been about 3 hours or so without issue.