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iMac Random Shutdowns (Overheating?)

T

txhockey9404

macrumors 6502a
Original poster
Feb 25, 2008
548
1
My first iMac Aluminum 20" 2.0ghz had a problem where it would just shut off completely as if the plug had been pulled, and then it would refuse to turn on for about a minute. It would do this more and more often as time went on until it would shut off every 30 minutes to an hour. Thats when I decided it was time to bring it to the Apple Store (a little late I know), where they tried to fix it 4 times with no luck. I was forced to go to the store 9 times in 7 days for the many problems it had. The first repair replaced the logic board and HDD blower(I think thats what it was, I know it was a blower of some kind), and when I got home, I tried to reinstall Tiger to start clean to see if that would help it. It shut off every time in my 9 attempts to reinstall the OS, so it had nothing to boot into. I then took it back to the store. That time, they replaced the logic board again and I took it home. When I got home, it wouldn't even turn on, so I took it back. The 3rd repair, they replaced the power supply, and when I took it home, it appeared to boot up, but the screen would not turn on, and it would not start an external monitor. So I took it back again. They tried to fix it again, but ran out of things to fix, and just gave me a new computer.

This new computer is the exact same model, except it had Leopard instead of Tiger. Recently it has started showing the same symptoms as the old iMac. It will occasionally just shut off, even when I am not doing very intensive tasks (listening to music in iTunes, Safari, iChat, etc), and it is not very hot (I try to keep my CPU and GPU temps under 70, any higher than about 67 I just turn the computer off). It is starting to become more frequent. Probably the two most intensive tasks I give it regularly are Handbrake and XPlane 8, and it will usually get very hot during both of these and sometimes shut down. I cannot seem to find any pattern in the shutdowns.

Here is what my console says when I search for "shutdown kernel" in the system.log

Jun 3 07:41:57 Alec kernel[0]: Previous Shutdown Cause: 3
Jun 3 09:16:09 localhost kernel[0]: Previous Shutdown Cause: 0 -This was one of the shutdowns
Jun 3 10:00:38 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 3 10:02:18 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 3 10:06:06 localhost kernel[0]: Previous Shutdown Cause: 0 -This was one of the shutdowns
Jun 3 11:08:46 localhost kernel[0]: Previous Shutdown Cause: 3
Jun 3 11:14:17 localhost kernel[0]: Previous Shutdown Cause: 5

I was just wondering if anyone else is having this problem, or knows a way to fix it. If you need more information just ask.

Here is a forum on the Apple support site, but no one there knows what it is either.
http://discussions.apple.com/thread.jspa?messageID=7308819#7308819
 
txhockey9404 said:
This new computer is the exact same model, except it had Leopard instead of Tiger. Recently it has started showing the same symptoms as the old iMac. It will occasionally just shut off, even when I am not doing very intensive tasks (listening to music in iTunes, Safari, iChat, etc), and it is not very hot (I try to keep my CPU and GPU temps under 70, any higher than about 67 I just turn the computer off). It is starting to become more frequent. Probably the two most intensive tasks I give it regularly are Handbrake and XPlane 8, and it will usually get very hot during both of these and sometimes shut down. I cannot seem to find any pattern in the shutdowns.
Click to expand...

If you are having the same problem with a new computer it may be time to consider external influences. Have you attempted to use the computer on a different wall outlet? Something in another room would be preferable for testing. Are you using any kind of surge protecter, UPS or switched outlet extension? One of these could flake out enough to cause a brownout or shutdown. Try plugging directly into a socket without anything between the computer power cable and the wall outlet.

Its unusual for a computer to make it out of the store operational several times then suffer an immediate failure when plugged in at home. I could see it happening once, but several is odd.

Hows your screen? If it looks good your lucks not all bad :)
 
I tried it on a different outlet in a different room without a surge protector with only a mouse and keyboard plugged in and it still shut down once after a few hours of use.

The screen on the new one has no visible problems so I guess I got lucky there :) The old one had 3 dead pixels and the gradient issue.
 
Re: iMac Random Shutdowns

Random reboots have been increasing on my iMac Aluminium 20" 2.4Ghz Intel Core 2 Duo (2GB Ram 750GB hard drive).

From my current system.log:

bash-3.2# egrep -i 'previous shutdown' system.log
Jun 8 09:14:13 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 8 09:23:51 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 8 18:29:37 localhost kernel[0]: Previous Shutdown Cause: 0
Jun 9 07:14:16 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 9 08:49:49 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 9 14:22:34 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 9 20:05:49 duncan-baillies-imac kernel[0]: Previous Shutdown Cause: 5
Jun 9 20:10:00 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 10 07:10:18 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 10 10:38:04 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 10 12:53:45 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 10 12:59:00 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 10 18:51:10 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 11 11:15:31 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 11 12:10:53 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 11 15:08:26 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 11 22:20:51 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 11 22:25:04 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 12 09:19:21 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 12 12:06:15 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 12 16:19:01 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 13 09:22:36 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 13 10:13:20 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 13 10:33:58 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 13 12:18:53 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 13 12:20:12 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 13 12:41:01 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 13 16:12:44 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 13 16:27:59 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 13 16:40:23 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 13 17:42:09 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 13 19:38:29 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 14 10:01:50 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 14 10:39:25 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 14 11:33:17 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 14 13:54:45 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 14 17:38:23 localhost kernel[0]: Previous Shutdown Cause: 5

No panic or crash logs, just "Bong".

Judging from this thread taking it to an Apple Store may not be a good idea. Will watch and wait...
 
txhockey9404 said:
I tried it on a different outlet in a different room without a surge protector with only a mouse and keyboard plugged in and it still shut down once after a few hours of use.

The screen on the new one has no visible problems so I guess I got lucky there :) The old one had 3 dead pixels and the gradient issue.
Click to expand...

Hate to say it, but another trip to the Apple store is in order then.
 
Working on a theory...

I have a hunch that the problem occurs after my son (4) has been playing some weird and wonderful internet games. His account was under parental controls and I have removed it for the timebeing while I investigate. The machine has not yet crashed while I have been using it, even for extended periods. I also wonder if the recent firmware upgrade may be a contributing factor. Could it be s/w or firmware being fooled into thinking the m/c is too hot or is it hardware related with some dodgy power track on a circuit?

I will use it heavily for a while to see if I can rule out my son's activity...

Duncan
 
Well it hasn't shut off for a while, but I have been going a bit easier on it lately. This week I get to do some video editing :), so I can see if I can get it to shut off from being under load.

Right now, I am restoring 2 iPods at once (iPod Touch 16gb and iPod 5g 30gb) and that usually makes it shut off, so I will report back if it does. Thank you for your help.
 
A cure!?

I just noticed some recent posts on the apple support discussion thread which say the cause is the 'Cable, DC, Power Supply/SATA/Inverter' (part number 922-8188).

Looks like folks who have had this replaced have been cured.

Duncan
 
I logged a call with Apple and made an appointment to take the machine in repair. I'm convinced the problem is as discussed in the apple support thread but when I mentioned that to the product specialised he said he was going to have the part numbers removed from the discussion! Helpful. Not.

Duncan
 
It shut down again

It shut down again

Here is my console log for the day with the search keyword shutdown in system.log

Jun 18 09:06:57 Alec ManagedClient[1811]: CGSShutdownServerConnections: Detaching application from window server
Jun 18 09:06:57 Alec com.apple.loginwindow[1800]: Wed Jun 18 09:06:57 Alec ManagedClient[1811] <Warning>: CGSShutdownServerConnections: Detaching application from window server
Jun 18 09:06:57 Alec ManagedClient[1811]: CGSDisplayServerShutdown: Detaching display subsystem from window server
Jun 18 09:06:57 Alec com.apple.loginwindow[1800]: Wed Jun 18 09:06:57 Alec ManagedClient[1811] <Warning>: CGSDisplayServerShutdown: Detaching display subsystem from window server
Jun 18 09:07:51 Alec kernel[0]: Previous Shutdown Cause: 3
Jun 18 09:51:03 localhost DirectoryService[11]: Improper shutdown detected
Jun 18 09:51:03 localhost kernel[0]: Previous Shutdown Cause: 0 <thats when it happened

I was just listening to music and browsing the internet, but about an hour before, I was doing some encoding for that video editing I mentioned earlier.
 
Power Supply Replaced

My latest news is that I dropped my machine off at the Apple Store this morning and they have replaced the power supply. I will keep you posted if that fixes the problem, or not.

Duncan
 
baildun said:
Jun 8 09:14:13 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 8 09:23:51 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 8 18:29:37 localhost kernel[0]: Previous Shutdown Cause: 0
Jun 9 07:14:16 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 9 08:49:49 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 9 14:22:34 localhost kernel[0]: Previous Shutdown Cause: 5
Jun 9 20:05:49 duncan-baillies-imac kernel[0]: Previous Shutdown Cause: 5
Click to expand...

Was the one with the shutdown cause zero the type of shutdown we are discussing? Because if it is, then we have found a commonality between the two occurrances, and we could pinpoint what the problem is. (If anyone here knows how to interpret the log entries.)

I really hope that the power supply that you are having replaced cures the problem. If that is it, I might give the Genius bar another try because I am a bit unhappy with Apple's service. On my first machine, the power supply didn't fix it, but who knows, maybe that was just a lemon.
 
I got another shutdown, this time while waking from sleep.

The log file said
Jun 22 09:31:50 localhost kernel[0]: Previous Shutdown Cause: 0

I am almost positive that shutdown cause 0 is the type of shutdown we are talking about. I had to shut the computer off by holding the power button to restart it, but I know that that did not affect the shutdown cause because when I held the power button again to shut it off, it gave me a shutdown cause of 3.
 
Looking good

I'm optimistic that the new power supply has fixed the problem. My machine has had no reboots or crashes since I brought it home from the Applestore on Thursday evening. I can't complain about the service from Apple...dropped off in the morning and picked up in the evening and (hopefully) fixed.

Duncan
 
That's great! Hope there really aren't any more problems so you don't have to keep going back. Mine has not had any problems for a few days, so its usable. Now if I could get my dud iPod Touch replaced.:)
 
Again!

It shut down again after being on for 2 days

Same log file

Jun 24 10:26:04 localhost kernel[0]: Previous Shutdown Cause: 0
 
Sorry to hear that. Maybe you should give the Apple repair another go. I took them an extract from my system.log as shown below and the output from "last" where you can see entries for Crash in the wtmp if users were logged in. If they replaced the PSU already that may persuade them to dig deeper into the machine.

Come to think of it, I have a history of power supply problems on my Macs. (Showing my age here) but I had a Powerbook 170 with power supply problems, a Powerbook 5300 with power supply problems, a G3 powerbook with power supply problems and this iMac with power supply problems. I've only had the one machine which didn't have power supply problems and that's a G4 powerbook.

Duncan
 
Wow all those bad macs almost makes you want to give up on them. But I never could because, although this is my first Mac, I could never go back. I had loved Tiger, and love Leopard even more. Despite all their problems, they are WAAAAAAAY better than any Windows machines I have had (Around 10). So I guess I'll just deal with it for now until I have the time to go back to the Apple Store.

Could you keep me posted on how your machine is working? If that really does fix it, I would like to go to the Genius bar with some knowledge.
 
baildun said:
I just noticed some recent posts on the apple support discussion thread which say the cause is the 'Cable, DC, Power Supply/SATA/Inverter' (part number 922-8188).

Looks like folks who have had this replaced have been cured.

Duncan
Click to expand...

This sounds so convent (and cheap) does it help (or is this the entire power supply ) ?
 
Is it not waking from sleep or actually shutting down?

We bought our iMac in Oct.07 before Leopard and then installed Leopard. It's been perfect until last week when we couldn't wake it from sleep... my husband thought it had shut down. The Apple Support said to unplug all power and then plug it back in and restart. That fixed it. We've been away from home for a week so I don't know if anything has happened... will check it later this week.

In the July '08 Macworld under Bugs&Fixes, they had a small article on "Never-Ending iMac Sleep". They said the SMC (System Management Controller) needs resetting. Hold power button down to actually shut it down. Unplug all cables including USB keyboard, etc. Wait 15 seconds. Plug it all back in and turn it on. They referred everyone to Macworld.com/3519 for details.

I just hope they are right and it doesn't happen again.
 
If it does keep happening, you could always take it to Apple and show them this forum as well as the one I linked to in my first post. Hopefully they won't give you as much trouble as they gave me. I think I just had a little bad luck there. I can test and see if the Genius bar service really is that bad this week when I go to take my iPod touch for repair/replacement.
 
I've had no random shutdowns since Apple replaced my power supply about two weeks ago so I am a happy man. The machine has been on constantly since then.

Duncan
 
i am now facing this problem. i also bring my imac to an apple althorised rapair center twice. but they said not problem found. but yesterday, this "shutdown" occured again when i am trying to burn a dvd, and my imac was very hot ( although it is in a air conditioning room ) due to hot weather. but today is a rainy day, i try to burn a dvd, NO SHUTDOWN this time, so i can say imac shutdowns randomly very possible cause by OVERHEATING !
 
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