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iMac shuts down, overheats?

#1 User is offline   SanDiegoMatt 

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Posted 15 December 2009 - 02:34 PM

My iMac (purchased spring of 2008, intel core duo processor, running windows using parallels) shuts off on its own periodically. It is not sleeping - this happens while I am working on documents. The screen goes black, the power is definitely no longer on. After 30 seconds or so, the power button will respond and I can restart it. I've noticed it always seems hot to the touch on the top/top back of the monitor at these times.

Several months ago when this happened, I held the power button in while plugging in the power cord because I had red that would cause the fans to operate at a higher speed and I thought this might help keep it cooler. That worked and I didn't have any problems with it shutting down, but then I read conflicting reports suggesting I would burn out the fan(s) if I let them run at this speed. The noise didn't bother me as it did some other posters, but I don't know what to believe anymore.

Any suggestions on 1) what the root cause is 2) whether/how I can fix the root cause (since I am fed up with losing work due to its capricious shut-downs) and 3) opinions on the fan speed issue?

Thanks for your help. I know some of you have already posted to similar discussions, but I would appreciate it if you would weigh in on the problem as I'm experiencing it.
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#2 User is offline   macnuke 

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Posted 15 December 2009 - 04:12 PM

how clean is your environment?
just might have plenty dust in it to start clogging vents and that will cause the overheat.
if it's all thru the vent and the fans are still moving air.. how noisy is it?
that would be more dust/dirt on your fans and mobo.

perhaps a good cleaning would fix it.
just a thought.. as always, your milage may vary.
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#3 User is offline   chas_m 

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Posted 17 December 2009 - 06:27 AM

View PostSanDiegoMatt, on 15 December 2009 - 02:34 PM, said:

My iMac (purchased spring of 2008, intel core duo processor, running windows using parallels) shuts off on its own periodically.


Did this always happen? Or just since you started using Parallels? Or just started recently and you've been using Parallels before? Do you have AppleCare?

If it's been happening since before the warranty expired, it's a pity you didn't get it seen to before the warranty expired.

Quote

After 30 seconds or so, the power button will respond and I can restart it. I've noticed it always seems hot to the touch on the top/top back of the monitor at these times.


The back top of an iMac is ALWAYS quite warm/hot to the touch. The iMac cools mostly by convection, so the heated air rises out the top slot.

Quote

Several months ago when this happened, I held the power button in while plugging in the power cord because I had red that would cause the fans to operate at a higher speed and I thought this might help keep it cooler. That worked and I didn't have any problems with it shutting down, but then I read conflicting reports suggesting I would burn out the fan(s) if I let them run at this speed.


Yes, the fans were not designed to run continuously at full blast. Bad idea.

Quote

Any suggestions on 1) what the root cause is


As the computer on Star Trek used to say, "Insufficient data." The first thing I'd try is to not run Parallels and see if that makes a difference. If it doesn't, try setting up a "virgin" admin account and see if the problem can be recreated in that account. This will help us determine if the problem is hardware or software.
Cheers
chas_m


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#4 User is offline   Michell 

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Posted 09 February 2010 - 01:39 PM

View Postchas_m, on 17 December 2009 - 06:27 AM, said:

View PostSanDiegoMatt, on 15 December 2009 - 02:34 PM, said:

My iMac (purchased spring of 2008, intel core duo processor, running windows using parallels) shuts off on its own periodically.


Did this always happen? Or just since you started using Parallels? Or just started recently and you've been using Parallels before? Do you have AppleCare?

If it's been happening since before the warranty expired, it's a pity you didn't get it seen to before the warranty expired.

Quote

After 30 seconds or so, the power button will respond and I can restart it. I've noticed it always seems hot to the touch on the top/top back of the monitor at these times.


The back top of an iMac is ALWAYS quite warm/hot to the touch. The iMac cools mostly by convection, so the heated air rises out the top slot.

Quote

Several months ago when this happened, I held the power button in while plugging in the power cord because I had red that would cause the fans to operate at a higher speed and I thought this might help keep it cooler. That worked and I didn't have any problems with it shutting down, but then I read conflicting reports suggesting I would burn out the fan(s) if I let them run at this speed.


Yes, the fans were not designed to run continuously at full blast. Bad idea.

Quote

Any suggestions on 1) what the root cause is


As the computer on Star Trek used to say, "Insufficient data." The first thing I'd try is to not run Parallels and see if that makes a difference. If it doesn't, try setting up a "virgin" admin account and see if the problem can be recreated in that account. This will help us determine if the problem is hardware or software.

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#5 User is offline   Earthling7 

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Posted 09 February 2010 - 01:51 PM

I know this. I have exactly the same problem with my early-2006 20" iMac. My bet is the power supply or a sensor that exaggerates the heat and causes the computer to shut down to protect itself.
I once had a signature with my Macs. Then Macworld updated their forums and my Macs went.
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#6 User is offline   Michell 

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Posted 09 February 2010 - 02:11 PM

HI, I just purchased my My iMac 27" November of 2009, intel core duo processor and out of the blue it just shut off. The screen went black and the colour wheel just sat there spinning, I tried to restart 2 or 4 times and ended up unplugging it and left it for 30 and then restarted and has been running fine for the past 30 min. is there a problem with the monitors overheating? should I be turning the computer off in the evenings whan I am done?

Thanks
Michell

View Postchas_m, on 17 December 2009 - 06:27 AM, said:

View PostSanDiegoMatt, on 15 December 2009 - 02:34 PM, said:

My iMac (purchased spring of 2008, intel core duo processor, running windows using parallels) shuts off on its own periodically.


Did this always happen? Or just since you started using Parallels? Or just started recently and you've been using Parallels before? Do you have AppleCare?

If it's been happening since before the warranty expired, it's a pity you didn't get it seen to before the warranty expired.

Quote

After 30 seconds or so, the power button will respond and I can restart it. I've noticed it always seems hot to the touch on the top/top back of the monitor at these times.


The back top of an iMac is ALWAYS quite warm/hot to the touch. The iMac cools mostly by convection, so the heated air rises out the top slot.

Quote

Several months ago when this happened, I held the power button in while plugging in the power cord because I had red that would cause the fans to operate at a higher speed and I thought this might help keep it cooler. That worked and I didn't have any problems with it shutting down, but then I read conflicting reports suggesting I would burn out the fan(s) if I let them run at this speed.


Yes, the fans were not designed to run continuously at full blast. Bad idea.

Quote

Any suggestions on 1) what the root cause is


As the computer on Star Trek used to say, "Insufficient data." The first thing I'd try is to not run Parallels and see if that makes a difference. If it doesn't, try setting up a "virgin" admin account and see if the problem can be recreated in that account. This will help us determine if the problem is hardware or software.

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#7 User is offline   chas_m 

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Posted 09 February 2010 - 08:16 PM

View PostMichell, on 09 February 2010 - 02:11 PM, said:

HI, I just purchased my My iMac 27" November of 2009, intel core duo processor and out of the blue it just shut off. The screen went black and the colour wheel just sat there spinning


Um, if the machine is shut off, then how can the colour wheel be present? Please try to use concise terms when describing problems, thanks.

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Is there a problem with the monitors overheating?


No, monitors don't overheat -- processors do. Which is not to say that this is actually the problem. Based on your vague description, its really not clear what the problem actually is.

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Should I be turning the computer off in the evenings whan I am done?


No, putting it to sleep is fine too.
Cheers
chas_m


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#8 User is offline   mrclavet 

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Posted 28 April 2010 - 04:31 AM

I bought my 20" imac in 2007 and it worked great until the spring of 2009 when the hard drive failed. I did not have applecare but did get the hard drive replaced. Ever since then, my imac will just turn off randomly as well. I am using OS 10.4.11, no windows parallel, and no taxing software (video rendering etc). The imac will just shut off when Im typing an email or typing in a document. Like others in this forum, I have to wait 30 seconds or so before I can turn it back on. It is VERY frustrating.

The environment it is in is very clean and I do clean the vents every week. It is really making me want to go back to a PC... there I said it. I know that is not a nice thing to say but it drives me up the wall.

let me know if you have any thoughts
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#9 User is offline   chas_m 

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Posted 29 April 2010 - 09:23 PM

View Postmrclavet, on 28 April 2010 - 04:31 AM, said:

I bought my 20" imac in 2007 and it worked great until the spring of 2009 when the hard drive failed. I did not have applecare but did get the hard drive replaced. Ever since then, my imac will just turn off randomly as well. I am using OS 10.4.11, no windows parallel, and no taxing software (video rendering etc). The imac will just shut off when Im typing an email or typing in a document. Like others in this forum, I have to wait 30 seconds or so before I can turn it back on. It is VERY frustrating.

The environment it is in is very clean and I do clean the vents every week. It is really making me want to go back to a PC... there I said it. I know that is not a nice thing to say but it drives me up the wall.

let me know if you have any thoughts


Even though its out of warranty, you should take it in to an authorised Mac technician and have them run tests. You can run the Apple Hardware Test yourself from your original restore DVD (just hold down "D" key when booting up with the DVD in the drive.)
Cheers
chas_m


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#10 User is offline   superadboy 

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Posted 14 April 2011 - 07:49 AM

Download this App for setting your iMacs fan speed because they run hot. Mine was locked up when I came in this AM and after doing some research I found out this was the problem. This App seamed to fix it. I set all fans to about 3000/rpm.


Here is the link
http://www.macupdate...9/smcfancontrol
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#11 User is offline   leeh 

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Posted 02 November 2011 - 08:55 AM

View PostEarthling7, on 09 February 2010 - 01:51 PM, said:

I know this. I have exactly the same problem with my early-2006 20" iMac. My bet is the power supply or a sensor that exaggerates the heat and causes the computer to shut down to protect itself.


Same problem here... and this is my conclusion too!

Currently my only option is to use SMCFanControl to blast the fans and monitor the temperature. The danger area seems to be around 70°C+. Sounds quite hot but my thought was the iMac was designed to run a lot hotter than that. Like you say it seems like an overly sensitive sensor is stepping in and cutting the power to "protect" the components. Perhaps someone who really knows the inner workings could give us some more info. If it is the case, it makes me wonder if it can be reccaliberated or ignored altogether (perhaps a little dangerous but I monitor the heat manually anyway and it's gotta be better than blasting the fans all the time / power cutting randomly). Preferably a software fix... but I understand that's wishful thinking lol. Would be great to get to the bottom of this.

I did once post on Apple's Discussion Forum but had no replies at all... :-(
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#12 User is offline   inductionloop 

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Posted 18 November 2011 - 11:33 AM

This all seems similar to my problem,

Imac 20" intel dule core early 2008

My mac shuts off after a period of moderate use like, watching a video on the net or using ableton live for a while. It will turn straight back on automatically but shut down again within a few seconds, the computer will work ok again after about 10 minutes (time to cool down?), i took it to the mac store and was told to replace the hard drive, this did not fix the problem also, i have replaced the ram, no difference again, the hard drive temp is about 36 degrees (not that hot)

I have noticed that the top left of the mac is hotter that the rest and it never shuts down when this area is cool ( maybe related? )

I have no idea what to do now, but i am sure it will cost some more money to fix, i am hope-in that it is the power supply as this costs about £69 (it looks to be as easy to replace as the hard drive).

?
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#13 User is offline   MichaelMorgan 

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Posted 22 November 2011 - 01:19 AM

This is my first post so I hope I am doing this correctly!

I have a similar problem. I have a 20'' iMac with the following spec:
IMAC 20/SD
Processor: 2.4GHz Intel Core 2 Duo
Memory: 2GB 667 DDR2 SDRAM - 2x1GB
*Upgraded to 3GB (2GB + 1GB) - 02/09/2011
1GB (one SO-DIMM) 667MHz DDR2 SDRAM (PC2-5300), supports up to 4GB
4GB Memory Upgrade (two 2GB)
1GB (one SO-DIMM) of PC2-5300 (667MHz) DDR2 memory
Two SO-DIMM slots support up to 4GB
Hard Drive: 500GB Serial ATA Drive
Optical Drive: SuperDrive 8X(DVD+R DL/DVD+RW)

Purchase Date: 09/2007

I usually leave the machine turned on. I put the screen to sleep when unused.

About 2 weeks ago, the machine became unresponsive and shut down. Starting up again brought up a folder with flashing '?'. Pressing the power button turned it off straight away.
1 week ago, it started up with no issues (I had not tried turning on for a few days). I opened disk utility and ran permissions and disk check - no issues? I then started a backup but when I left the machine for a few minutes, I came back and it had turned off. I could not restart straight away but it did start up after a few minutes. Now I get the apple logo and the spinning wheel and doesn't do anything else. I need to press the power button for a few minutes to turn off and cannot start straight away.

Any help would be appreciated. Even point me in the right direction. It doesn't look like hard drive issue. Should I open and clean out fans etc?
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