MegaSack DRAW - This year's winner is user - rgwb
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STW hive mind, lend me your ears:
I have a 2017 27" iMac (3.8GHz Intel Core i5) that randomly turns itself off.
The screen goes blank and the machine is dead. It will not restart unless I unplug it from the mains, leave it for 30seconds or longer and then plug it in again.
The problem started a couple of months ago and does not appear to follow any pattern. Sometimes it will run for several days without shutting down but sometimes it can happen 2 or 3 times an hour.
I have searched the web and there are numerous accounts of a similar problem but no one seems to have come up with a cause or remedy apart from replacing the internals.
Has anyone here had the same issue and managed to resolve it?
Overheating could cause this... is the fan still working properly?
Had a similar problem ages ago with one of mine, think the fan was playing up and not coming on when it should? Cannot 100% remember unfortunately!
I know I downloaded some kind of monitoring app... again can’t remember which one, just googled and I don’t think it was this (would’ve remembered downloading Fanny 🤣) but it seems to offer the same functionality.
https://fannywidget.com/
You can monitor CPU/GPU temp & manually crank up the fans if required.
Course, it could be something completely different!
D9 you have loads of stuff in the USB Ports?
I had a Mac mini that hadn’t been vacuumed out for a while and it needed clean8ng and a change to an external powered USB hub toget rid of the overheating/ current draw problem.
I have discounted overheating as the problem can happen within a couple of minutes of turning the iMac on in the morning. Fanny installed to keep an eye on the temp though, cheers.
I have also unplugged all peripherals as I have read of people experiencing USB ports causing a similar problem. However, the problem didn't go away.
I have made sure all the airways are clear and used a small vacuum cleaner to make sure there is no dust or fluff in them.
if the fan’s not working or it’s something like not enough thermal paste between CPU & heatsink then it’ll overheat & shutdown very quickly. Might be worth using the monitoring app just to rule these out. (Would be good news if either were the problem tho as easy fix!)I have discounted overheating as the problem can happen within a couple of minutes of turning the iMac on in the morning.
If it's shutting down for thermal protection I'd expect to see something to that effect in the console logs. If the logs are empty then I'd deduce that it's shut down so quickly it couldn't write to the log so possibly a PSU problem?
If it's a Fusion Drive machine this may have some pointers https://discussions.apple.com/thread/8655305
Is the iMac in a dusty room? Is there a way you can ascertain if the cooling fan and any cooling fins are maybe clogged up with dust? e.g. evidence of dust or fluff build up at the entry to the cooling intake?
Run diagnostics and see if it tells you anything.
Power it down fully. Press the on button. Hold down the 'd' key. Wait a bit. It will enter a menu that looks a bit like Internet Recovery. Select a language, and let it run. Anything amiss?
@codybrennan - Diagnostics reports no problems found. I have also run EtreCheck and that hasn't found anything either.
@wobbliscott - Not particularly dusty. However, I will vacuum out all the vents to make sure they are clear. I don't think it is an overheating problem though as running Diagnostics today is the first time I have heard the fans kick in.
Here's a link to investigating shutdown causes:
https://georgegarside.com/blog/macos/shutdown-causes/
If you enter the following command in Terminal;
log show --predicate 'eventMessage contains "Previous shutdown cause"' --last 24h
And see if there's a number after "Previous shutdown cause". (Mine was cleanly shut down yesterday, and so I see a code of '5').
Thanks, @codybrennan
That is showing a few causes:
0 - Power disconnected. Could be a power supply problem. 4 instances of this.
-128 - Unknown. Possibly linked to RAM. 2 instances of this.
3 - Hard shutdown. 1 instance.
5 - Correct shut down. 1 instance.
I have now vacuumed out all the ports and vents, removed and reseated the RAM modules and unplugged everything except my time capsule so I'll see what happens and run the Terminal command again if the machine shuts itself down.
I wonder if I have got a failing PSU in the iMac?
Could be, but definitely worth doing a PRAM and SMC reset first. And obviously check the mains supply.
Got in touch with Apple today and they advised doing everything I have already done.
Final recommendation was to back up the machine and then call them back so they can wipe it and reinstall the OS. This will then help to determine if the problem is S/W or H/W related.
It took me 9 hours to do a back up because the bloody thing kept crashing part way through a back up. Finally got a complete back up, went back on to the Apple tech help site and I can’t get a call back until Saturday.
Latest update for anyone who may be interested:
After a couple of calls with Apple Tech support, running all the diagnostic checks and disk utility I was advised to completely wipe my iMac and do a fresh install of the OS. Did that yesterday and for a few hours all seemed good. However, the fault has reappeared and my iMac has crashed 3 times today.
I haven't re-installed any files or programs so that discounts the problem being software related.
If it is a hardware issue, and all the evidence now points to that, I am stuffed as current lock down restrictions make a store visit impossible and I am left with an £1,800 desk top ornament!
Anyone got any advice or pointers that may help me, please?
You can still get Apple to repair it, as they can arrange courier collection & return - https://support.apple.com/en-gb/repair. I’ve had two MacBook Pros repaired out of warranty in the last 12 months by third parties - StormFront ( https://stormfront.co.uk/) and more recently, TC Touch Solutions ( https://www.facebook.com/tctouchsolutionsuk/ or https://tctouch.co.uk/) , when StormFront were on long lead times. Both have a diagnosis charge.
Good luck!
Thanks, @drlex.
I'll see what say on Tuesday and take it from there. Both sites bookmarked just in case.