iMac Randomly Shuts Down -Overheating Problem?

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Level 1

2 points

iMac Randomly Shuts Down -Overheating Problem?

I've posted in these forums once before about my iMac randomly shutting down. I believed I had solved the problem by following another users instructions which were as follows:

"Machines that are just randomly shutting down are usually caused by defective hardware. The only thing that can be done about that is to call Apple and have it replaced or serviced. There is probably not any one particular solution as it could be any number of the internal components failing and the resulting symptoms could be the same.

If you'd like to do some hardware tests yourself before calling Apple that can be done. First try resetting the SMC: http://docs.info.apple.com/article.html?artnum=303446

Next insert the original gray install disk, restart your iMac, then hold down the "d" key until it boots up into the Apple Hardware Test. Run the extended test.

Also if you have Apple Care install TechTool Deluxe from the cd provided. Then run TechTool on your system."

I also removed and replaced of a defective external HD that I thought my be causing problems. But after all these steps, the machine kept turning itself off.

I had read in some forums that it was due to the internal temperature of the iMac. So I downloaded smcfancontrol 2.1 and increased the fan speed on the internal fans. This did bring down the temperature as revealed by the iStat Pro widget. However, I still had another shutdown.

So I turned off the machine, went to bed, and this morning when I turned it on iStat Pro said these were the internal temperatures of the iMac:

CPU A 77 degrees F
GPU 85
GPU Diode 88
GPU Heatsink 85
Ambient 61
Memory Cont. 74
Airport Card 112
HD Bay 1 76

I find these numbers to be unbelievable. Especially the airport card. When the whole system seemed to be running hot, the Airport Card said it was 122. It always says something above 100 degrees. The other temperatures also seem out of whack. How can the CPU be 77 degrees after 10 hours of being completely powered down in an office environment that is only 55 degrees?

Has anyone else run into a similar problem?

Has anyone else found the problem to be a faulty temperature sensor (and is there a way to reset it, or does it have to be replaced)?

Overheated? in Oregon...

Message was edited by: OregonMac7

iMac (Intel 20") & MacBook (Intel), Mac OS X (10.5.1), iMac (2.4 Ghz, 320 GB), MacBook (Base Model)

Posted on Feb 18, 2008 9:29 AM

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Answer 1

Feb 20, 2008 6:15 AM in response to OregonMac7

I have gone through months of troubleshooting a white 17" Early 2006 iMac for this exact same phenomenon. With no AppleCare, I resorted to opening the case myself. I found that replacing the power supply didn't solve it, but rather, it was the DC-in plug on the logic board that was loose. I have not had any problems since reseating it. The aluminum iMacs' DC-in to the logic board is accessible from the side of the logic board rather than the rear as in the white iMacs. My theory was that the DC connector vibrated loose as it does not have a clip securing the connector or that the worker didn't get a good connection as the logic board has to be very close to the chassis to plug it in and takes some maneuvering. This won't likely apply to the Aluminums, but just wanted to share. Just as a note, opening your iMac will most likely void your warranty, so let Apple take care of it.

My thread is linked below if you haven't gotten to it. Really nothing new on there. I still get posts here and there. Good luck, and everyone follow up! It's the only way to keep us all informed.

http://discussions.apple.com/thread.jspa?threadID=1088454&tstart=0

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Answer 2

Feb 18, 2008 4:10 PM in response to OregonMac7

Are those temperatures in Celsius or Fahrenheit? If they are in Fahrenheit then they are actually quite low and perfectly normal for a cold boot. After it's been on for a while then the temperatures will increase a bit. Check to see whether your temps are being displayed in Celsius or Fahrenheit.

The iMac will go into a forced sleep mode if the CPU temp ever reaches 100 degrees Celsius.

George

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Answer 3

OregonMac7 Author

Level 1

2 points

Feb 18, 2008 5:20 PM in response to George Peters

Hey, again, George.

The temps are in Fahrenheit, not Celsius.

The Airport card being at 121 degrees running temperature doesn't seem a bit high to you? I'm no engineer, so I'm not certain of the average running temperatures.

Also, do most iMac problems of this nature seem to fall more into the 20" models than the 24" models, or are both experiencing this problem? If the 20" units are the problem, I'm tempted to just take this one back and get a 24" unit.

Do you think, George that it's a problem with a faulty heat sensor?

Best regards,
Lee

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Answer 4

OregonMac7 Author

Level 1

2 points

Feb 18, 2008 6:07 PM in response to OregonMac7

George:

You'll be interested to know. I just put in a call to Apple Care and they are sending me a program to collect stats that they're going to give to Apple Engineering. Apple is acutely aware of the problem, and it's occurring in both 20" and 24" iMacs.

They said after they get my data that they'll contact me and provide next steps information.

I'll be curious to hear what they prescribe for a resolution. I'll keep this thread posted. Perhaps their answer can help others.

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Answer 5

Feb 18, 2008 10:55 PM in response to OregonMac7

Just to add to this topic out of many - one person said Apple is "acutely aware of the situation". If they are, they didn't tell me when I asked the question point blank "Is this a problem Apple is aware of?" "No, this is fairly unique to you" was the response.

I finally called in my random shut off problem. I waited to see if 10.5.2 somehow fixed it, which it didn't. I was also only 5 days away from the end of my complimentary support period. I've been having this problem since the day my iMac was delivered - completely random, sometimes I could go a week or so without a problem, then on some days, 2, 3 shutdowns.

I was disappointed to find out I would have to truck the machine in for "repair" at a local depot, with no idea of how long it would be away. This is my only computer right now (other than an old notebook), so being without it for an extended time will cause problems

Because of this, I bought AppleCare for it, paying $200 so someone would come to my house to fix it. They say they're going to most likely swap out the logic board. Somehow, I don't know if that will fix it, but we'll see. I'll pick the brain of the service tech to see if he's aware of this as a common problem. Given the number of threads here about it (dozens and dozens), I can't believe Apple isn't aware of it. But my service call person, very friendly and polite, at least acted like it was unique and a "never heard of before" problem. She ran me through the stages others have had (run SMC reset, run diagnostics), etc., and as all of us with this problem know, it doesn't fix it. And it's hard to tell, at least while on the phone, if it does or not, because it's a *random*, unpredictable problem.

I'll report back after the service tech visit.

Mark

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Answer 6

Feb 19, 2008 1:21 AM in response to OregonMac7

No those temps are fine quite cool actually because 121F = 49C and usually when discussing internal computer temps more often then not they are measured in Celsius. All the temps I've posted have been in Celsius. So I doubt you have an over heating issue.

Like I said before if your machine is shutting down randomly and everything you have tried did not fix the problem then it's most likely a hardware defect. Apple will have to take care of the problem. Keep in mind it could be any number of things causing your problem and your iMac may exhibit the same symptoms. This makes it very difficult to say that all the such and such iMacs have certain problems when in fact they could be totally different things causing the issues. One reason for this is most of the internal components are part of the logic board including the graphics processor. So lets say the GPU was the cause of your problem Apple would have to replace the whole logic board. A GPU failure could cause your machine to randomly shut down. But then again so could a Power Supply problem or bad RAM.

I'm glad that you called Apple and got a support ticket going. Hopefully they will be able to fix your machine without too much trouble. Make sure to back up your data before you take it in just to be safe.

George

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Answer 7

OregonMac7 Author

Level 1

2 points

Feb 19, 2008 9:57 PM in response to CoffeeGeek

Hi, Mark:

The technician that I spoke to really, truly did say that Apple is "acutely aware of the problem." And also added that it wasn't just the 20" iMacs, that he had just gotten off a support call with someone having the same problem with a 24" iMac.

I look forward to hearing what your technician says. I've yet to hear back from Apple on this (I've sent them the data file they requested).

Either way, I think we're all pretty clear on this: something is wrong with these machines. I'd love it if it were a software fix. But if not, I'd love to simply know so we can get our machines fixed.

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Answer 8

OregonMac7 Author

Level 1

2 points

Feb 19, 2008 10:00 PM in response to George Peters

Hi, George:

Great advice on possible problems causing the shut downs. I have to say though, it's amazing how many posts I've read having this same problem. I'm equally amazed that Apple -- who's products are typically notable for being exemplars of quality -- would let these machines out with this many problems being reported.

I am backing up my HD with Time Machine, so I should be OK in the long run. I'm also lucky in that I have a MacBook I can fall back on if this needs to go in or be returned.

Best regards,
Lee

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Answer 9

Feb 19, 2008 11:12 PM in response to OregonMac7

While I do agree with you as most people including myself have very high expectations of Apple products and find it disconcerning to see all the negative feedback here. However let me point out that this is a support forum and naturally the majority of people that post in these forums are having some kind of issue. With that said there is no way to really gauge whether this is even a lot of people having the same problem or not. We have no idea how many iMacs that are at home working perfectly compared to how many complaints get posted here.

George

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Answer 10

Feb 20, 2008 1:48 AM in response to OregonMac7

Certainly sounds like a case of the left hand not knowing from the right, huh 😉

Well, I have my call in, and I am getting onsite service to replace the logic board, as per Apple's recommendation.

I'm reading the other longer thread (171 replies), and it's disheartening to hear how some of the "geniuses" are handling this problem. They can't replicate it by leaving the mac running overnight, so "the problem doesn't exist". Hello! It's *random*! As in, not easy to replicate!

I'm also a bit disillusioned that the popular Mac sites (TUAW, etc) haven't picked up on this story yet. I emailed TUAW the link to the long thread, and they ignore it. Usually when this gets more "mainstream" press, then Apple finally steps up, acknowledges a problem, and serious fixes are made. Right now, it's a bunch of complainers (me included) in some threads on the Apple site.

I took a huge leap last November, and went from PCs to the Mac platform, after working on my personal migration plans for a month prior - how to move from my photo editing on the PC to the Mac (I wasn't about to buy another full copy of Photoshop, for eg, but I did find out I could upgrade from Win PS to Mac PS), if all the programs I use for photography and design were available on the Mac, learning the ins and outs of shortcut keys, how things are done, etc etc, and was so happy initially when I got the Mac and said goodbye to the PC.

Now I'm literally afraid to do any serious work on the Mac for fear of the "pulled plug" syndrome losing the last 20, 30 minutes of work I've been doing because I didn't save every 2 minutes. And iLife's Pages doesn't autosave (much to my chagrin), so I've lost some long correspondence and articles typed because I didn't save it before the pulled plug o' death.

Not a very nice computing experience.

As a suggestion, maybe everyone reading this and the other thread can flood TUAW.com with a news suggestion to cover this problem. Engadget, Gizmodo too while you're at it. I think once these million-viewers a day blogs cover it, we'll see some real action from Apple.

Just a thought....

Mark

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Answer 11

verdejt

Level 1

42 points

Feb 20, 2008 11:44 AM in response to Euripides

Well I just got my iMac 20" on the 8th of Feb and agree that they do seem to run hot. I was reading on another post about concerns for overheating and they recommended loaded a program that allows you to increase the internal fan speed. I have had this program running for about 10 minutes and noticed a drop of almost 10 degrees C. I only increased the fan speeds by about 300 RPMs.

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Answer 12

Feb 20, 2008 2:06 PM in response to CoffeeGeek

I don't really think it's that big of an issue because these machines are covered under warranty and Apple will fix the problem if you call them. I mean it suckz when you get a faulty computer but hey it happens and you can't really complain because you are getting an on site repair. Once your machine has been fixed you shouldn't have any problems. True all "Geniuses" are definitely not created equally so you're probably better off calling Apple support directly than taking it to a Genius.

George

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Answer 13

OregonMac7 Author

Level 1

2 points

Feb 24, 2008 1:38 AM in response to George Peters

Hey, everyone:

Well, AppleCare responded with a solution. As George pointed out, my iMac shutting-down problem is likely related to a hardware defect. After they received my log file data, they contacted me and let me know that I should take my iMac back into the Apple Store for a replacement. Which I did today.

Thank God for Time Machine. For those of you without a backup HD, GET ONE! It made putting my replacement iMac back together a snap. That being said, interestingly the Mac Geniuses did not say they received many of these iMac shut down returns. However, the AppleCare rep did say they've heard a lot of this happening.

Regardless, my iMac has been running beautifully since I got it today -- but it's only a day!

I'll post again in a week or so. My old iMac never lasted that long before shutting down. If I make it to Friday, I feel I may be home free.

I will note, however, that I am still running smcfancontrol 2.1 just to be sure.

Until later,
Lee

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Answer 14

xmdsys

Level 1

5 points

Feb 24, 2008 9:51 PM in response to OregonMac7

My suggestion to anyone with these issues is try installing smcFanControl. Increase your minimum fan speeds anywhere from 300-1000rpms. I increased mine and it made a 25c difference in the power supply. I was experiencing shutdowns during burning single layer dvds. Installed a temp. monitor program, noticed the power supply was reaching 85c during burning (thats just too hot). After bumping up the min. fan speeds the power supply never passed 60c and I haven't had a problem with sudden shutdowns while burning (and i've been backing up data literally all day). The fans should be kicking up before the power supply is reaching 85c, plain and simple. This hardware just needs a little extra air flow to keep itself from baking itself broken.

So, if you're having sudden shutdown issues give smcFanControl a shot and keep an eye on your power supply. It's more likely the problem will be with that than any other piece of hardware.

And I think george is the one who said I should get it fixed anyway because it shouldn't be doing that. But, I simply can't afford to be without my imac for any extended period of time and I don't have an apple store around. So if it's just a temperature issue, I think this is an easy fix that I can live without having to get my imac replaced. Most likely it isn't a hardware issue as much as it is an issue with the fans not speeding up when they should.

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Answer 15

OregonMac7 Author

Level 1

2 points

Feb 25, 2008 7:46 AM in response to xmdsys

XMDSYS:

Although I used smcfancontrol on both the iMac that was shutting down and my new one, I'm inclined to believe George's advice: get any malfunctioning iMac repaired or replaced because the error is likely caused by faulty hardware.

The faulty hardware may or may not be exacerbated by temperature problems, but in my case, I've come to learn that temperature had nothing to do with it.

I never reported here, another interesting set of actions by my iMac in addition to random shut-downs. When docking my iPhone, iPhoto & Pages would launch unsolicited. There were other oddities, but nothing that made me believe they were related to my shut-downs.

Now that I have a new iMac (that appears to have no such malfunction problems), I have not a single one of the problems I had before. No shut downs, no random application launches. MOST NOTABLY (and this relates to your advice on smcfancontrol): the temperature specs on my new iMac are identical to the one that was a problem. Not a degree of difference.

So, I'm inclined to agree with George's original advice: if your iMac is shutting down randomly, it's probably a hardware defect. If you're under warranty, take it back. In my case, the Apple Store was extremely accomodating. They didn't even bat an eyelash to exchange it for a new one. Bottom line, get a replacement or take it to get it fixed. No one should have to deal with a bad iMac.

I will return to report on how my iMac is doing at the end of the week, but as I reported earlier, since Apple replaced it with a new one, I've not had a single problem. I ran it pretty hard yesterday for nearly 12 hours; it ran flawlessly.

I think having smcfancontrol is a good idea - it's a nice utility that helps ensure your components don't get too hot. But I don't think it's the solution to these random shut downs (in most cases). I believe it's a bad component or circuit somewhere in the machine.

I know it stinks to be without your machine while it's being fixed, but losing my work when it was shutting down on me was even worse. I'd bite the bullet and get it fixed. Or, as I said, get it replaced if you're under warranty.

Best regards,
Lee in Oregon

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