2017 iMac Random Restarts (5k, 580pro)

[QurazyQuisp]

Hi all,
Yesterday, while in bootcamp playing a game, my iMac completely shut down out of nowhere. Since then, I get random restarts which seem to be associated with heat.

I have:
- Removed all accessories (USB, etc)
- Reset SMC, PRAM (is this still a thing?)
- Removed all the ram, put just one in, had same issue, put a different stick in, same issue.
- Run Apple Diagnostics, nothing returned
- Made sure computer is completely up-to-date

The reason why I say it seems to be associated with heat is because it'll happen after leaving the computer on for a while, or playing a game for a little bit. Once it happens, the frequency goes up considerably up to the point where it won't even power on. Then, after leaving it alone for a little while it'll work fine for a while then start the cycle all over again.

It's not a kernel panic as it happens in windows and osx alike and just goes straight to the "off" state (can even hear the HD click)

I have Macs Fan Control installed and nothing seems out of the ordinary. Also, the fan doesn't seem to kick into high gear before it happens, so I'm not entirely sure. "GPU Proximity is definitely the hottest at 55 degrees C and going up. I've attached a screenshot. I have logging going on, but nothing really of note beyond: "[2019-02-03 09:15:46:008] [thread 5677] [SMC/Service.cpp#630] WARNING: getTemperature - skipping sensor TPCD with value of 129"

Sadly I'm just barely out of warranty and given the wonderful state of Apple Genius Bar, I don't really want to bring it in if the default is going to be "bad logic board" when really it's just too much thermal paste or something similar.

Anyone have any guesses?

 

[MandiMac]

Is it an i7 machine? What game were you playing while this happened?
Normally, CPU and GPU throttle if the cooler can't cool the components down as it's needed. So my best guess would be the PSU that reached a spike - and remember if you got the i7 AND the 580, you have the absolute maximum for what that iMac is built for, speaking of thermals and electricity needs...

 

[QurazyQuisp]

Is it an i7 machine? What game were you playing while this happened?
Normally, CPU and GPU throttle if the cooler can't cool the components down as it's needed. So my best guess would be the PSU that reached a spike - and remember if you got the i7 AND the 580, you have the absolute maximum for what that iMac is built for, speaking of thermals and electricity needs...

It was GTA online, but it’ll do it with taxing stuff in macOS too.

 

[MandiMac]

It was GTA online, but it’ll do it with taxing stuff in macOS too.

Okay, another shot: If your fan is staying at 1200 rpm, there's something off. If it goes up to 2700 rpm, everything is fine here. Is it always when you're doing taxing things, as in can you replicate the behaviour?

 

[QurazyQuisp]

Okay, another shot: If your fan is staying at 1200 rpm, there's something off. If it goes up to 2700 rpm, everything is fine here. Is it always when you're doing taxing things, as in can you replicate the behaviour?

Yes, that’s what starts it, but after it gets hot it’ll do it for any reason (even if down to idle). I’m not sure what the fan curve should be, but it takes a while for the fans to speed up.

 

[MandiMac]

Yes, that’s what starts it, but after it gets hot it’ll do it for any reason (even if down to idle). I’m not sure what the fan curve should be, but it takes a while for the fans to speed up.

Okay this sounds good so far. If the fan goes up to 2700 rpm or so, everything is as intended.
Again for your crashing problem: Please specify which processor you have and if it keeps crashing even if you don't do taxing things.

 

[QurazyQuisp]

It’s the i5, not i7. And I don’t think it crashes with non-taxing things, but honestly haven’t really tried it. The issue started on Friday/Saturday and after Sunday I’ve just left it sitting unplugged.

 

[xgman]

Have you looked at your system log in console app to see if you can check what was going on at any particular crash time listed?

 

[MandiMac]

It’s the i5, not i7. And I don’t think it crashes with non-taxing things, but honestly haven’t really tried it. The issue started on Friday/Saturday and after Sunday I’ve just left it sitting unplugged.

While unplugged, hold the On/Off button for 10 or more seconds, then try again. Maybe use some test cases, like light Pages editing, surfing the web and so on for a few minutes. Then switch to more taxing things, maybe booting into Bootcamp and play a game or two. It would help tremendously for diagnostics; then again, I'm still on my first thought that your PSU took a hit there.

 

[QurazyQuisp]

So, I did the 10second unplug thing, and plugged it back in and went into macOS, then windows and... it crashed when playing again. Notably the fans DID not speed up, and as soon as it restarted and I was back in macOS the cpu temps were showing over 100 C. They quickly cooled down once the fan picked up in macOS. So I do think it's a thermal thing, I just can't figure out why in macOS it's crashing too when I know the fans speed up...

 

[mreg376]

Apple will have to figure that out. Consider it an expensive lesson learned as to why people buy AppleCare.

 

[MandiMac]

Sadly, there's no more options left. Seems like it's really a fried logic board or something ... just tell Apple, maybe they're showing some love to a loyal customer. And about AppleCare: I have it for all my devices, and I use them heavily. As I had exactly 0 problems so far (aside an iPad Air that had a faulty GPU I recognized in about 2 weeks), one could say AC is wasted money on my side. All the best to you, OP, I know that can be frustrating - but going the Apple route is way better than have a computer you can't really use...

 

[QurazyQuisp]

I'm going to open it up and re-apply the thermal paste. It's well known that Apple over-applies and temps suffer because of it. I throttled the fans with macs fan control and haven't experienced a crash since, so I kind of doubt it's something actually wrong with the circuitry.