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On boot, iMac Apple logo blinks red after update to Mac OS Sierra

After upgrading to MacOS Sierra, my 2015 iMac 21.5 Retina has a blinking red Apple logo and then a brief splash of screen flicker when booting. Once booted, the computer seems to run fine, with no obvious flakiness. I'm not sure why the logo blinks red and then the screen flickers -- bad drivers; a software fault in the boot phase; some issue with the fusion drive; or perhaps some other gremlin? A quick internet search reveals that at least a few others have the same issue with this OS version, and it seems to have happened in years past with other MacOS version upgrades. But there are no good answers on how to fix it. I've rebooted several times hoping it would clear itself, but no luck.

iMac, macOS Sierra (10.12), iMac 2015 21.5 4k Retina

Posted on Sep 22, 2016 7:48 PM

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74 replies

Oct 15, 2016 9:31 PM in response to Mike Rose1

Thanks Mike. Apple surround turning RED IS WELL DOCUMENTED. I also have at shut down a missing PROGRESS SPINNING WHEEL. Hard to tell if the computer is shut down. Also discovered, FREQUENTLY VISITED FAVOURITES will not show up at all. CAPTURE DATA WAS PLACED ON MY COMPUTER AND SENT TO APPLE for them to correct the software problem. Since dealing with APPLE I have yet to experience this product to run without issues. Dear APPLE ENGINEERS.... Create, Test then Share. It is now up to Apple.

Oct 17, 2016 8:38 AM in response to Headhunter06

Apparently just a Sierra anomaly, according to several people who have asked Apple - to be fixed in an update. I have it too and it doesn't seems affect anything.

Oct 17, 2016 8:39 AM in response to Headhunter06

Not actually a 'problem' as far as I can tell. Apparently just a Sierra anomaly, according to several people who have asked Apple - to be fixed in an update. I have it too and it doesn't seems affect anything.

Oct 19, 2016 6:39 PM in response to Headhunter06

Something a little different...spent a few hours with apple supprt on the phone and the conclusion was faulty hardware on the iMac 4K. This is a recent purchase for me and they advised to return. We tried resetting the ram, repairing the disk, and then ultimately a wipe and clean install of OS Sierra. None of which resolved the issue. Disappointing because I pay the Apple price premium because they usually work really well...

Oct 26, 2016 6:43 PM in response to Headhunter06

My brand new 21.5 Retina was bought in august....it blipped red once last week on startup...and things seemed to be running fine. When I tried to install the latest bug fix, it bricked my system. Starts up just fine, chimes...then turns black, back on, blips red...then looks like a corrupted spinny wheel of rainbow colors for a couple seconds...then goes black. It will turn on in recovery mode, but not safe mode. I ran disk utility....reset PRAM blah blah blah....nothing. I have an appointment on saturday....and this thread is not helping my confidence...Remember when it was so exciting to get an upgrade? Now, straight anxiety.

Oct 26, 2016 8:46 PM in response to Headhunter06

To all IMAC FANS of late running Sierra. Why would APPLE put Sierra out on the market to cause so much problems. Are they starting to slip? When running a business , if this type of a failure occurred I would have to overhaul staff and techniques. What are they doing? I do not know what a good running APPLE feels like. I like the system but not the results. !! GET THIS PROBLEM FIXED OR REPLACE. ENOUGH IS ENOUGH.

Question marked as Helpful

Nov 1, 2016 8:46 AM in response to Headhunter06

So, I tookmy imac to the Apple store on saturday....and something seemed to work...though, it blows my mind. The initial clean install of seirra wouldn't work....but going back to el capitan did. The guy I worked with seems to think the problem has to do with the 2TB Fusion drive in the imac.....something about breaking it apart...and sierra not being able to put it back together. I don't know that much about fusion drives...but that might be a reason...and might be the common denominator in this thread. So, for now....I'm not upgrading back to Sierra....I'm staying with El Capitan for at least 6 months. Why would anyone release an update like that? Now I need to disable the annoying...."DO YOU WANT TO UPGRADE?" notification.

Nov 1, 2016 5:11 PM in response to aliciafromkansas city

Alicia and EVERYBODY ELSE THERE IS NOTHING WRONG WITH ANY OF YOUR COMPONENTS IN "EL CAPITAN."ONLY IN "SIERRA". I ALSO ARE DEBATING TO LEAVE "SIERRA" AND GO BACK TO THE FUTURE WITH

EL CAPITAN" UNTIL THEY GET THIS FIXED." Frequently Visited Sites does not work properly. I only got one site to show, that is it. I don't have a rotating wheel at shut down either. ??

On boot, iMac Apple logo blinks red after update to Mac OS Sierra

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