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iMac quits without warnings, then reboots… sometimes a number of times. Suggestions

atlanticza

atlanticza

macrumors 6502a
Original poster
Jul 18, 2008
563
2
Cape Town
It’s a iMac 27-inch (mid 2011) running Sierra that’s misbehaving. So I’ve run the Apple Hardware Test - no problems found. I’ve reset Pram and SMC. It doesn’t appear to be any Apps that’s causing it, as it may reboot without any Apps open. I’ve disconnected most peripherals attached to it… still no cure. (And some time ago I had a faulty AMD Radeon HD 6970M replaced under Apple warranty.)

The only common thread when this crash/rebooting occurs is when it’s woken up after sleeping all night long. After that, it’s mostly stable for the rest of the day. So, all in, I haven’t a clue why this is happening. Any help or suggestions would be most appreciated.
 
Could be the new graphic card failing, how old is it?

Could also be the SATA cable failing, as it would also cause those symptoms. I have had it fail in the exact same model, so it does happen. If you have an external drive you can boot from for some time, you could find out if that is the problem.
 
Thanks for this. the graphics card was replaced mid 2015. And I'll certainly consider booting from an external drive. Thanks again.
 
I have 12 GB installed, hardware tests and Rember reported no faults with it. But it was my initial thought too.
 
You could try if it occurs also with a newly created user. If it doesn't happen there it might be software related.

Also you may try Etrecheck and post the report here. http://etrecheck.com

It could show what might be wrong with your Mac mostly software wise.
 
Tried all suggestions and eventually took it into an Apple service centre. Tested for a week there. No problems and could not repeat the "fault" so it's back with me and appears to be OK. Mysterious.
 
Again, I'd suspect the RAM.
Is the RAM that's in it now the "factory original"?
Or... has it been replaced?

If it's been replaced, do you still have the original RAM?
Have you tried putting it back it, and running that way?

Have you tried taking the RAM out, cleaning the contacts, and replacing it?
 
Hi, Apple supplied the RAM and it's new. And when I took the iMac in, they gave everything a thorough clean, and could find nothing wrong even after hours of stress testing... so I'm holding thumbs...
 
... well holding thumbs wasn't enough: it's doing it again! Seems to not like being woken up from Sleep mode after pressing Esc early in the morning. After a couple of reboots it's happy for the rest of the day. Strange. Could it be a peripheral like its wired keyboard?
 
Try creating a system on an external HD or partition and run off of that for awhile. My guess is a kernel problem.
 
OK, so the stability lasted about an hour, then back to square one. However I'm pleased to report that the graphics card has been replaced again... the nasty Radeon HD 6970M. That was the trouble. But all appears to be working now. Thanks for all your suggestions.
 
atlanticza said:
OK, so the stability lasted about an hour, then back to square one. However I'm pleased to report that the graphics card has been replaced again... the nasty Radeon HD 6970M. That was the trouble. But all appears to be working now. Thanks for all your suggestions.
Click to expand...


spookily this is almost identical to my situation which I posted about last week.

I also have a 27" imac 2011, bought in 2013, its also had the 6970m replaced by apple, as well as the screen which failed at the same time. that was probably 18 months ago but id have to check.

just in the last week, its started restarting randomly. sometimes I'm using it, once it did it 3 times in 10 minutes, but then it often runs a whole evening without problems. I always leave it on 24/7 and I can tell its sometimes done it when its unattended as I have left an app open and its closed when I go to the computer and I had to log in too.

I posted last week and people said it was maybe because I was using a beta of high sierra, so ive ordered a thunderbolt SSD (as well as a new usb hard drive and a thunderbolt to usb adaptor) and was thinking ill put up with it until that arrives and I can do a clean install (non beta) on there.

however I'm starting to worry its the PSU as this morning I plugged my iPhone in to charge and it beeped as normal, and then beeped every few seconds, so effectively, charging, not charging, charging, not charging...

hope its either software or the graphics card as if its the PSU and I have to pay for it, then the cost of that plus the thunderbolt SSD and adaptor and new usb drive would have been a good way towards the cheapest 21" model and the thunderbolt bits will be useless if I have to buy another mac.
 
madeirabhoy said:
spookily this is almost identical to my situation which I posted about last week.

I also have a 27" imac 2011, bought in 2013, its also had the 6970m replaced by apple, as well as the screen which failed at the same time. that was probably 18 months ago but id have to check.

just in the last week, its started restarting randomly. sometimes I'm using it, once it did it 3 times in 10 minutes, but then it often runs a whole evening without problems. I always leave it on 24/7 and I can tell its sometimes done it when its unattended as I have left an app open and its closed when I go to the computer and I had to log in too.

I posted last week and people said it was maybe because I was using a beta of high sierra, so ive ordered a thunderbolt SSD (as well as a new usb hard drive and a thunderbolt to usb adaptor) and was thinking ill put up with it until that arrives and I can do a clean install (non beta) on there.

however I'm starting to worry its the PSU as this morning I plugged my iPhone in to charge and it beeped as normal, and then beeped every few seconds, so effectively, charging, not charging, charging, not charging...

hope its either software or the graphics card as if its the PSU and I have to pay for it, then the cost of that plus the thunderbolt SSD and adaptor and new usb drive would have been a good way towards the cheapest 21" model and the thunderbolt bits will be useless if I have to buy another mac.
Click to expand...
[doublepost=1520417940][/doublepost]Sounds like the 'movie' I went through. As I mentioned before, the faulty graphics card was not picked up by the most stringent hardware tests. It was only when I mentioned - on my third visit - to an Apple Service Provider that it could be the card that they eventually agreed and replaced it (despite being a 'vintage' machine). So far, the iMac has behaved very well with the latest OS installed. Wish you well because I know how frustrating it can be.
 
atlanticza said:
[doublepost=1520417940][/doublepost]Sounds like the 'movie' I went through. As I mentioned before, the faulty graphics card was not picked up by the most stringent hardware tests. It was only when I mentioned - on my third visit - to an Apple Service Provider that it could be the card that they eventually agreed and replaced it (despite being a 'vintage' machine). So far, the iMac has behaved very well with the latest OS installed. Wish you well because I know how frustrating it can be.
Click to expand...

the worst outcome for me would be its the power supply. ideally its software related and goes away, next one is its the graphics card and apple replaces. but to pour more money at it will be a major pain.
 
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