Imac Shutdown

as some of you may recall, about 2.5 years ago (or so) I had an issue where my 2012 27" iMac would run for a while (minutes to hours) and then abruptly shutdown. Unplugging it for a few seconds, and it would restart and repeat the pattern… After months of fighting with Apple service, they finally replaced (supposedly) both the logic and graphics boards… Since that time it had run flawlessly… Until today.

Now when I attempt to reboot it… 90% of the time, it gets 1/2 way thru the inital progress bar, and shuts down, sometimes it gets the dock displayed, waits about 20 seconds with the rainbow pizza and shuts down.

Now here is the strange part. If I boot in SAFE MODE… it runs just fine (and has been for an hour or so)… I notice a few things (custom fonts for example) are not activated… but the point is… the computer is running…

Anyone have any ideas on how to trouble shoot this?

Here is what I am in the process of already doing

  • making a bootable copy (SuperDuper!) of my LAPTOP which has Sierra on it (the iMac has ElCap)
  • once created… will see if it shuts down when attempting to boot from that copy… If not, it would be an internal drive problem, if so, then I have NO IDEA, unless it i s an issue with the graphics card, and loading a particular driver kills it (SafeMode doesn’t load all drivers)

Steps to be sure…
First remove all the external devices from imac.
Second unplug the power for 1 min.
Plug the power cord
Wait five seconds, then press the power button to turn on your Mac.
Reset the nvram on imac
Reset nvram
Run the diagnostics from apple…
apple diag page
One last i forget to write.
Check the ram,i don’t know how much ram installed on imac,but if you have 8,12,16 try to remove them and stay with 4gb (One module) ram to see if the module of ram is ok…

Is possible the pram battery have low charge or defect…

graphic card (what model is it on your mac ?) dead again…
safe mode does not load the graphics card drivers.
you can boot from another drive to confirm the bad thing.
in apple service center, we have a special program to test it without using the mac system
pretty sure it’s that graphic card failure.

also do you have an ssd drive or mechanical hard drive ?
if ssd it’s very unlikely a drive failure.
if mechanical it can also be a drive failure. then booting on an external drive should tell you.

Is possible Jean …

[quote=322209:@Jean-Yves Pochez]graphic card (what model is it on your mac ?) dead again…
safe mode does not load the graphics card drivers.
you can boot from another drive to confirm the bad thing.
in apple service center, we have a special program to test it without using the mac system
pretty sure it’s that graphic card failure.

also do you have an ssd drive or mechanical hard drive ?
if ssd it’s very unlikely a drive failure.
if mechanical it can also be a drive failure. then booting on an external drive should tell you.[/quote]

Model Name: iMac
Model Identifier: iMac13,2
Processor Name: Intel Core i7
Processor Speed: 3.4 GHz
Number of Processors: 1
Total Number of Cores: 4
L2 Cache (per Core): 256 KB
L3 Cache: 8 MB
Memory: 8 GB
Boot ROM Version: IM131.010A.B0A
SMC Version (system): 2.11f16
Chipset Model: NVIDIA GeForce GTX 675MX

I am doubting a drive failure, since Safe Mode boots just fine… perhaps a corrupted driver
1TB mech HD… no fusion, no ssd

I am cloning my laptop to test booting the iMac from an external drive…
If that works… I will see if I can clone the desktop drive to another disk drive… that MIGHT point out unloadable files… keyword “Might”

Have reset the SMC dozens of times, as that is the ONLY way to get it to reboot at all when it shuts down

The symptom of the 20 sec boot + rainbow i have this in my customer and was hdd failure…
Download this Smart utility
boot at safe mode and run it,will give the exactly hdd status…

[quote=322218:@Loannis Kolliageorgas]The symptom of the 20 sec boot + rainbow i have this in my customer and was hdd failure…
Download this Smart utility
boot at safe mode and run it,will give the exactly hdd status…[/quote]
or also drivedx utility will be more detailed, and the demo works for 14 days.
https://binaryfruit.com/drivedx
it will give you a percent of the disk “real” speed compared to a new one,
and also a percent of disk “failure” state very pertinent.
it scans all the internal counters of a SMART system, and can prevent you months before a big failure.

btw Dave, a ssd today is really something to work with ! it’s not cheap but once you have it you dont want to go back…

to be honest, I have a 2011 imac with almost the same failure as you describe at work,
and after some tests I ordered a graphic card ( it was already changed in december)

am doubting it is HDD problem… as I connected an external bootable drive cloned from my laptop, and it shut down at about the same point in the process… so I’m thinking it bombs when it attempts to activate some hardware feature during bootup that is NOT invoked during SafeMode…

DriveDX says 0 issues found… Health 97.4% Performance 97.4%, and all other indicators are either 0 (good) or 100% (good)
so I guess the HDD is probably not the problem… Sending me back to think graphics card.

Which I really cannot afford to fix (going on 16months unemp :frowning: ) … but I have to have this computer, as it is my only connection to potential employers etc.

I may have to just put it on a shelf until there is $$$, and hope I can survive with a slow laptop instead… sigh
another stressor that I really don’t need in my life right now :frowning:

bad news: it seems the graphic card is not available without the logic board … (although iFixIt remove it in the picture above …)
in europe it would be some 500€ + labor + taxes …

I don’t thing this issue will be graphics card…
Graphics card will have glitches or rainbow horizontal-vertical colours before the apple logo show up !!
If you don’t have that then the issue is not a graphic card from my opinion…(I know because before one year i have this problem with graphic card)
From the other side if was a thermal problem then the problem will be on the safe mode too.
Try this press ALT on the boot and see if the boot disk and recovery disk show up.
Stay there for a minute if there is no shutdown then for sure is no graphic card…
If you have backup from disk then enter recovery mode and format the hdd and make a clean install.

I agree a thermal would be in all boot modes…
its not HDD, as an external drive boot did the same thing, so any other backup would not boot either
its not a corrupted driver, as this would not be duplicated on an external drive made from another computer
and don’t you mean OPTION not ALT for dual boot mode? there the internal drive, a recovery drive and my external drive show up

and if its not the graphics card as you believe… what could it be?

FYI… I ran the Apple Diagnostics and it past with flying colors.

I know the situation and how bad you feel now because i was in the same situation before!!
Yes you have right is the option key…
I am trying with you to figure out where will be the problem.
The confuse part is on the safe mode the mac working without issues…
The apple diagnostics when i have the problem with my graphics card have passed 100%…
Maybe you have done but have you reset the pram? >cmd +option +P +R until the mac boot 3 times?
Try to boot with one memory module if you have 2 swap the modules etc…
Just to eliminate all the others before we make any conclusion.

[quote=322236:@Loannis Kolliageorgas]Graphics card will have glitches or rainbow horizontal-vertical colours before the apple logo show up !!
[/quote]
not necessarly. it can be completely black, it can work normally and black screen just before asking for login where the graphic card gets initialized.

it’s because the apple diagnostics does not use the graphic card the way the os x uses it.

[quote=322241:@Loannis Kolliageorgas]Try to boot with one memory module if you have 2 swap the modules etc…
[/quote]
yes that test has to be done before going to the graphic card. it’s easy and can save a lot of money !

Not sure if this helps. See whether your iMac is one of these models. The article was referring to iMacs sold between May 2011 to Oct 2012:

https://9to5mac.com/2013/08/16/apple-opens-graphics-card-replacement-program-for-some-mid-2011-imacs/

[quote=322280:@Cho Sing Kum]Not sure if this helps. See whether your iMac is one of these models. The article was referring to iMacs sold between May 2011 to Oct 2012:

https://9to5mac.com/2013/08/16/apple-opens-graphics-card-replacement-program-for-some-mid-2011-imacs/[/quote]
no it’s the previous model. I’ve changed dozens of graphic cards on these …