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Jul 23, 2016 7:38 AM in response to Lagoiskiby FranFox,A new shutdown today. I left my iMac working with iTunes and XCode for a minutes and... ¡boom!
Thanks to TG Pro I saw the temperature log. My normal CPU core temp was between 42 and 52 Cº, at the moment of the shutdown up to 63 Cº and keep at this for a while after the reboot.
I'll try to buy a couple of USB Fans to try to freeze a bit more. Any suggestion about other fan or cooler system for the iMac?
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Jul 23, 2016 8:09 AM in response to Leutrim Sby ElBartolomeo,hi to all, the shutdowns seem to disappear if i set monitor and hard disk sleeping mode to 3 hours (preferences/energy saving).
could you try this setup and report if your shutdowns will stop?thanks.
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Jul 23, 2016 8:10 AM in response to ElBartolomeoby FranFox,It's weird but I've tried. I'll let you know
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Jul 23, 2016 8:21 AM in response to ElBartolomeoby FranFox,Hi! I've tried but the shutdown occurs again Good news! I think I found how to reproduce the problem!
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Jul 23, 2016 8:30 AM in response to Lagoiskiby FranFox,Hi everyone! Good News! I think I found a way to reproduce the shutdowns! This is fantastic because if we can reproduce it we can solve the problem!
Following the theory of CPU overheating (or other component overheating) I make the following steps to force a shutdown:
- Install any fan software to see what's your CPU normal temperature (I'm now between 42-52 Cº in my CPU core 1 sensor).
- If your software allows to you to increase the fan speed. Disable this option, we want to force a overheat so make your fan as slow as you can
- Open as many programs as you can (And see how the temperature is growing).
- Finally, open any 3D game to force a little more the CPU.
See how your CPU temperature is growing, when the CPU exceeds 65º then you will have your shutdown.
Please guys, could you try to reproduce this steps and take note of the highest temperature of your processor?
I hope this time we've captured that awful gremlin.
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Jul 24, 2016 4:59 AM in response to Lagoiskiby FranFox,Another way to reproduce the problem for me is trying to reset NVRAM. When I try it (using the Command (⌘), Option, P, and R. when chimes) it shutdown and don't start again at least after 15 minutes...
How to Reset NVRAM on your Mac - Apple Support
Could you guys reset your NVRAM without problems?
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Jul 25, 2016 5:57 AM in response to FranFoxby ElBartolomeo,It's true. This is compatible with software problem for me....
But why it doesn't appear in log file?
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Jul 29, 2016 12:25 PM in response to ElBartolomeoby ElBartolomeo,D'oh....
if it works a little bit over internet surfing, it shut down too.....
iMAC = garbage!!!!
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Jul 29, 2016 2:12 PM in response to mattwithcatsby stjohns,Hello all, here is my story and so far, my solution to the Imac shutdown saga.
I also have the iMac (27-inch, Late 2012)
Processor 2.9 Ghz Intel Core i5
Memory GB 1600 Mhz DDR3
Graphics NVIDIA GeForce GTX 660M 512 MB
1TB Fusion Drive
Purchased computer 01/2013. As of 07/11/2016, out of the blue like so many others, my computer started shutting down randomly. I ran the AHT test and the error code stated that my hard drive was failing. I took my computer to the Genius bar and after they tested it, they came up with the same issue. They kept it for a few days and replaced my hard drive ($160 including tax and labor). For the next week, my computer was like new again. However, on 07/25, the issue returned. After reading these posts, I was reluctant to take it back to the apple store because it is a pain in the neck to lug this thing back and forth. I tried everything I could to avoid that trip. However, just for the heck of it, I decided to download the macs fan control from the previous post: http://www.crystalidea.com/macs-fan-control. The main fan RPM minimum is: 1200 - 2640 (max). I set it to 1500 and watched it. I also read in one of these post that if the CPU goes above 65, the the computer would shut down. What I have noticed is that ever since I installed the fan control, and started to notice which programs cause the temp to rise, my computer has not shut down and the back of my computer has been cooler.
Now I am not sure if this solution will work for everyone, but I must say, so far, it has worked for me. I noticed that chrome and safari used alot of memory, so i switched to firefox. Once again, so far as of today, I haven't any shutdowns in two days. Of course, time will tell because this issue seems to rear its ugly head whenever it wants to. I will keep you posted as to how long I go without a shutdown. I am keeping an eye on the fan control temps as well as the activity monitor that is built into the Imac.
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Jul 29, 2016 3:38 PM in response to Lagoiskiby Glasguy,Specs:
- Mac (27-inch, Late 2012)
- 3.4 GHz Intel Core i7
- NVIDIA GeForce GTX 675MX 1024 MB
Here i am adding myself to this forum as my out of warranty iMac is also experiencing intermittent shutdowns. Like most other folk on here, after the shutdown I can power my machine backup after disconnecting and reconnecting to mains outlet.
Having noticed that the intermittent shutdowns would happen when using Parallels or occasionally when browsing Internet, YouTube or listening to music.
I used Temperature Gauge and Cinebench to test and investigate. I noticed that my processor was running very hot! Cores running as hot as 103 oC . The temps for the power supply look good.
Since the iMac is out of warranty and I have a background in hardware repairs I decided to get my antistatic mat out and open the iMac for inspection.
Beware of the dirty mac :-)
So this is possibly why Temperature Gauge is showing high temp readings. The components are covered in heavy dust --> ( Fur jacket ) The heavy dust on the components won't help with cooling or airflow and possibly is related to the intermittent shutdowns.
Using an antistatic brush I cleaned the components free from dust and also applied thermal paste on the CPU and GPU.
It's as good as new looking after a good clean. I then fixed the LCD panel in place and ran more test using Temperature Gauge and noticed an improvement in cpu core temperatures whilst running CineBench.
I will run more tests later to see if the intermittent shutdown problem persists.
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Jul 29, 2016 4:01 PM in response to Glasguyby NickFromLE,Maybe you can help me in disassembling my imac, i just wasnt brave enough yet...
Have the same problem, in my case its Safari. Whenever i do not use Safari I dont have these restarts. When I start using Safari and just go to Energy Saving Mode, the iMac wont come up again. Its just down. I have to unplug and wait...
It would be nice if you can give me directions of how to get off the display. Maybe via PM.
Thanks!
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Jul 29, 2016 8:14 PM in response to Lagoiskiby mattwithcats,A Shop Vac and a can of air work for me without taking the case apart.
First, use the crevice tool and run around the entire case, especially the vent holes.
Now take a warm can of air and shoot air in, with the crevice tool next to where you are shooting.
Keeps dust from getting deeper in the machine, and getting in your house.
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Jul 30, 2016 4:08 AM in response to mattwithcatsby Glasguy,I read other posts where others used a can of air and vacuumed around external vents and the problem still persists.
Possibly you may not have had much dirt.
Having opened up my iMac as per pictures posted, I can say that vacuuming or using air around the vents on the exterior of the iMac will not do much to get rid of the deep dust that's buried within the fan and other places. That dust on the fan is hard and mud like in appearance. It took me some time to scrape and brush that dust out of the fan. Having excessive CPU temperatures, opening up the iMac also allows me to apply thermal paste.
So far my iMac has not experienced any shutdown, I'm still testing. I noticed that my iMac would shutdown within a period of two hours when running Parallels Virtual machine and using safari.
Today I'm running two Parallel virtual machines, one of these virtual machines have 2hr YouTube video playing, the other is installing Windows 8 updates. I also have YouTube Video on Safari and iTunes playing.
I'm stressing the machine more than I normally would during normal use and so far no system shutdown and temps are in a good range. I ran CineBench a few times parallel with these applications and no shutdown.
I find it interesting that so many people have this problem and logic board or power supply replacements have not solved the problem. Or in some cases users report that after having a Power Supply or Logic board replacement the iMac operates for a length of time only for the problem to resurface.
Do Apple service technicians clean the thick dirt from the machine before testing ? The dirt in the fan area will restrict the cooling, if the cooling is not sufficient then components are going to overheat and fail or become tempermental.
I initially though that this was a problem with the Power Supply or CPU. So far so good after cleaning components and applying thermal paste to CPU and GPU.
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Jul 30, 2016 5:03 AM in response to NickFromLEby Glasguy,I'm assuming your iMac is out of warranty.
Have a look at IFXIT YouTube for Teardown guides. Don't skip the antistatic mat if you decide to proceed. Be calm and careful ( Power Supply will hold a lethal charge when DISCONNECTED from mains ) and pay attention to how the cables disconnect from the logic board, i.e. pull or lift.







