IMac shuts down

My wife's iMac (24 inch, 2008) running OS 10.6 turns itself off during the night despite my having set sleep to Never in the energy saver. What else could do this ?

If it is losing power sometime during the night and "Start up automatically after a power failure" is unchecked, then it will stay off until you restart it.
Which by the way might not be a bad thing, because it is better than having the iMac shutting off and then restarting in the event that you are having power issues.
First re-check all your electriclal connections and ensure that the power is staying on to the iMac all night, then reset the iMac's SMC to see if that helps.
Intel-based Macs: Resetting the System Management Controller (SMC)
1. Shut down the computer.
2. Unplug the computer's power cord.
3. Wait fifteen seconds.
4. Attach the computer's power cord.
5. Wait five seconds, then press the power button to turn on the computer.

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IMac shut down suddenly and won't boot back up

This morning my iMac shut down suddenly. All I had open was Google Chrome and I was just on Facebook and that's it. When I tried to boot it back up, it wouldn't load past the startup sound, wherein it would appear to shut back down,or at the very least the screen would go black (my mouse has lights that stay on when the computer is on, and the light kept going on and off while the screen remained black). This was the case for at least a half hour until it suddenly booted itself back up all on its own. I had it on throughout the day, just browsing the internet and watching Youtube. It shut itself down twice during the day, and both times it restarted on its own right away after showing me a grey screen with the Apple logo and a progress bar. Now it just shut itself down again and it won't make it past the progress bar screen - if it even makes it that far, sometimes it shuts off right after it makes the startup sound. It keeps trying to boot up on its own over and over again, but it keeps shutting down right away. All the fixes I've searched for so far require a computer that actually boots up all the way so I don't think I could run any reports if I tried!
I'm running the latest version of Yosemite (10.10.2?).
Model number A1311
Not entirely sure what specs are useful to know so I'm just gonna write some of what's on the box it came in:
3.2 GHz Intel i3 processor, 4MBshared level 3 cache
4GB of 1333MHz DDR SDRAM
1TB serial ATA hard drive
ATI Radeon HD 5670 graphics processor with 512 MB of GDDR3 memory
Bought it around fall of 2010. Not sure if it's worth trying to get it fixed (I live nowhere near an Apple store) or if I should just get a new computer, but I would like to know what's wrong, if possible.

Try to boot into the Recover Partition by holding down the Command + R keys on startup. If it still won't boot then the HD has probably crashed. The is likely a AASP in your area, you can locate one by clicking AASP Locator, take it to one to be professional diagnosed. If it's only the HD, assuming you have been backing up, restoring to a new HD is pretty simple.

IMac shuts down when using Safari 2.0.4

My iMac shuts down when I visit certain websites such as Pogo or video sites. Took it to the Apple store and of course the problem wouldn't replicate there. They kept it to check out the scripts and logs to see if they could find a problem - without success; although they did suggest my house is haunted. Brought it home and it quit again.
We thought perhaps we were getting interference from other wireless devices and unplugged our cordless phone which worked for a day. The computer always turns back on so its more of an annoyance than a real problem, but I'm baffled.
It also happened once when I was downloading from the iTunes store, but is most prevalent with Safari.
We have wireless internet connected via ethernet to an Airport Express.
Any ideas? Thanks.
iMac G5 Mac OS X (10.4.10)

Hi Barry -
Yes I do live near a ghost town (kinda) - Virginia City, NV. And I did tell any unwanted visitors to leave.
Actually, in the last year, they have replaced the Super drive, power supply, inverter and logic board. The only reason I'm not thinking power issues is that it only happens when I'm in Safari or iTunes. I would use Firefox except I've got java issues with that. I can (and do) use the machine for other things all day long without problems. I can use Safari all day long as long as I'm not playing on Pogo or certain video sites. Maybe Pogo is haunted?
It also doesn't happen on my husband's iMac on the other side of the house. Is there something that could cause enough interference to actually make the machine shut down? Oh, the antennae for the satellite TV and internet are on the roof directly above me, if that would have anything to do with it.
Thanks for your help.

IMac shutting down on startup - Can't enter safe mode as wireless keyboard doesn't connect quickly enough

Hi all,
I was planning to use bootcamp to install Windows 7 on my mid-2010 21.5" iMac.
Bootcamp recommended I usk disk utility to repair the drive. I had a snow leopard install disk in the drive, (I didn't realise Lion already had it's recovery tools built in to the hard drive.)
Disk utility said it can't repair the drive and recommended I start backing up my data (because the hard drive could be about to fail). Fine, so I restarted, with the intention of backing up everything (all my work for the last 12 months). So I press the power button, grey screen comes up, then the apple logo, then a progress bar appears (found this odd at first, but later found out it has something to do with disk utility and a bad hard drive) it gets to around 20% and then all power is cut from the iMac and the hard drive stops/everything powers down.
Now, I can't seem to get my iMac to boot into recovery utilities or into safe mode because it doesn't connect to the wireless keyboard in time before it shuts down. So, if I use a wired keyboard (I have a dell USB keyboard that I can take from the office), will I be able to boot into safe mode?
Also, if the disk in drive is causing the problem, then I can't remove it because the wireless keyboard won't connect/register any keypresses.

Ok so, status report:
Wired keyboard is non responsive when I plug it in before/during boot. So i guess it needs to be plugged in before the iMac shut down. That's that out the window.
Plugged in headphones and I can't hear the startup chime so don't know when to start holding buttons.
To make matters worse, the wireless keyboard is no longer paired with the iMac, getting a green blinking light which indicates it wants to connect to a computer or device.
So I can't enter any commands whatsoever, can't remove the disk in the drive or boot safe mode. It's my worst nightmare.

IMac shuts down after removing Mini DisplayPort to SVGA

Hi,
The last couple of years I have worked with a 27 inch iMac in combination with a HP 27 inch monitor. This monitor is connected via a Mini Displayport to SVGA connector. Because I am going to use this external monitor anymore, I disconnected it today which made my iMac shut down imediately. Then it keeps rebooting and trying to start up but shuts down again. Over and over.
The problem stops as soon as I connect the monitor again.
Anybody have any thoughts?

Hello there, TheCapGuy.
The following Knowledge Base article is a great resource for steps in troubleshooting spontaneous restarts:
OS X: When your computer spontaneously restarts or displays "Your computer restarted because of a problem."
http://support.apple.com/kb/TS4636
Thanks for reaching out to Apple Support Communities.
Cheers,
Pedro.

First Gen G5 iMac: Shuts Down In Just Seconds

My first generation G5 iMac shuts down within about 30 seconds to several minutes upon boot up. I had it off for about 3 or 4 days days while away, prior to this it worked fine. I purchased it in November of 2004.
OS 10.4.8
I have it connected to an APC UPS, there was a lengthy power failure while I was away, but the iMac was off; it is connected to the UPS via USB cable, i've disconnected all unnecessary connections, opened up the iMac and blew dust out of it, but it still shuts down shortly after boot up.
Any suggestions would be appreciated.
Thanks!
1.8 GHZ 20 G5 iMac (Rev A) 1GB RAM/250GB HD Mac OS X (10.4.6)

Thanks all, and to Barry & MGW:
It looks as if my iMac is within the serial no. range of a recall for power supplies. My wife is taking the iMac to an Apple store today, she called Apple earlier this morning and got an appointment, also we have the AppleCare plan and are still covered. I will post again after the Apple Store visit with an update.
I use SuperDuper! It's a great program, unfortunately my last back-up is several weeks old (shame on me) and now the iMac won't stay on long enough to make a fresh backup.
Hopefully, a new power supply will fix things up and the HD will be untouched.

10.9.5 my iMac shuts down when supposedly asleep

How can I stop my iMac shutting down when it is programmed to sleep. 10.9.5

How can I stop my iMac shutting down when it is programmed to sleep. 10.9.5

Imac shuts down when not in use

I purchased my 21.5" imac July 9, 2011 with Snow Leopard. No problems for 1 month. Then about August 12th or so, my imac started to mysteriously "shut down" when not in use. I'll be working on it, then get up to go pour myself a cup of coffee or something...then I come back to my computer that has now shut off. It is NOT asleep...it is OFF. So I turn it back on and it is fine. This has happened a few times now within a week. Anyone else have this problem?
By the way, I am now running Lyon, as of August 18th. When the imac shut down, I was usually viewing photos or on the web.
thanks!

First thing I would try is to reset the SMC, it can help with power related problems. Shut down the Mac and unplug everything including the power. Press and hold down the power button for 10 seconds. Plug in the computer but be careful not to press the power button as you are plugging it in. Wait a few seconds and turn it on. Hopefully it won't happen again. There is always Apple Support. Don't let the problem persist until your free phone tech support has expired (3 months). I would also recommend using the iMac with an UPS, and at the very least, a high quality surge protector.
If you have MS Word or a similar word processor you could try enabling the autosave feature and set it to 1 minute intervals. Keep a document open and if you come back to the computer and it has shut down, you can look at the last time the document was updated and know what time the comptuer turned itself off. It could be useful in diagnosing the problem.

IMac shuts down when commanded to print

A friend of mine got a new Samsung color laser and when he tries to print his computer immediately shuts down. I uninstalled/reinstalled the printer software, ran FSCK which fixed some disk directory problems (probably from the unexpected shutdowns) and ran Cocktail, which did the cron scripts and cleared out the caches as well as repairing permissions. It seemed to be working normally, but he just called to tell me that the machine shut down again when he tried to print a document.
Anyone have any ideas about what's going on and what to do about it? Thanks in advance for your assistance.
PowerMac G5 2.0 DP Mac OS X (10.4.10)

Thanks for all the help.
I went back to his house tonight and we figured it out. I reset the SMU and installed the latest drivers, but the problem persisted. It was a little warm in the room, so we turned on a small fan on his desk next to the iMac. The next time we tried to print, we noticed that the speed of the fan dropped for a moment at the same time the iMac shut down. I then looked to where the equipment was plugged in and found one of those battery backup power strips with the printer plugged in to one of the backed up outlets. I moved it to one of the non-backed up outlets and the problem disappeared. I'm thinking that the printer was pulling too much power from the system and the iMac was shutting down due to low voltage. Just proves you have to check everything.
PowerMac G5 2.0 DP Mac OS X (10.4.10)

New iMac shutting down and starting up randomly

My new iMac shuts down and starts up at random (over and over again usually in the first few minutes of start up). I ran a test with the TechTool Deluxe and the test involving "video" failed (all other tests passed). What do I do now? Help!!
Thank you!

Welcome to Discussions - if your iMac is new, it's an intel and you can post on their forum, they'll be able to he you better. However, your first thought should be to call Apple, you have 90 days of free telephone help, and a year's warranty. Since what you are describing sounds like a hardware problem, even if you 90 days are up, call Apple (they will provisionally charge your credit card, but will remit the charge if the problem is hardware related). They will take care of the problem.

My imac shuts down unexpectedly and now a fan is running??

Hello,
I have been working on my iMac all morning and it shut down twice within a half hour and I had to press the start button on the back to get it going again. Now their is a loud fan running and I have no idea what is going on. Help much appreciated. Thanks in advance!

Hi ebeugs,
Thanks for visiting Apple Support Communities.
If your iMac shut down unexpectedly, and the fan is running unusually fast or loud, you may need to reset the System Management Controller.
I recommend following this troubleshooting method:
Before Resetting the SMC
Try each of the following steps in this order before you reset the SMC. Test the issue after completing each troubleshooting step to determine if the issue still occurs.
Press Command + Option + Escape to force quit any application that is not responding.
Put your Mac to sleep by choosing the Apple () menu from the upper-left menu bar and then choosing Sleep. Wake the computer after it has gone to sleep.
Restart your Mac by choosing the Apple () menu from the upper-left menu bar and then choosing Restart.
Shut down your Mac by choosing the Apple () menu from the upper-left menu bar and then choosing Shut Down.
If the iMac unexpectedly shuts down again, or the fan continues running unusually fast or loud, follow these steps:
Resetting the SMC for Mac Pro, Intel-based iMac, Intel-based Mac mini, or Intel-based Xserve
Shut down the computer.
Unplug the computer's power cord.
Wait fifteen seconds.
Attach the computer's power cord.
Wait five seconds, then press the power button to turn on the computer.
You can find these steps and more information about resetting the SMC here:
Intel-based Macs: Resetting the System Management Controller (SMC)
http://support.apple.com/kb/HT3964
Best Regards,
Jeremy

Imac shut down

My imac shuts down by itself at anytime

First check System Preferences - Energy Saver - Schedule and see if someone accidentally scheduled shut offs. If that is unchecked then you probably have a power issue, get your power and plugs checked where the machine is located, if the machine is on a UPS and the power issue is cause by your wiring or power company then the UPS can at least make it easier on teh system so it can do orderly shutdowns.
If the power checks out OK then run Apple Hardware Test in extended mode at least 3x, if errors appear you have verified a hardware problem and need to take the machine in for repair. Don't ask what the codes mean, Apple does not publish that information. AHT is not the most reliable test but it's what you have, if it doesn't report errors that does not rule out a hardware issue, meaning you should still take it in to be checked by your local Apple Store or AASP.

Imac shuts down w/o reason

Recently I face the problem that my iMac shuts down without any reason, just like unplugging the the power. I did check the power, it's ok. Sometimes it happens after some hours, sometimes just after start-up.
Does anybody know about that?

Hello Fred:
Your profile does not indicate what version of iMac you are running. Take a look at this to determine if your system falls into one of the categories:
http://www.apple.com/support/exchange_repair/imac.html
Barry

Imac shuts down, randomly, all the time

So my imac shuts down randomly all the time, after it turns itself off, u need to unplug it for ages, then it will restart (way longer than it should to reset smc). Even in target mode,
Even stranger is it logs a console message stating, system must shutdown now, shutting down....
I thought it must certainly be hardware issue but what? I have checked all temps, reset firmware, etc etc.....
The logic board has been replaced, so it can only be the psu?? any ideas?

I've experiencing the same problem.
If there is a power failure (or the power line gets disconect) I have to unplug everything from the back of the computer and wait for hours till I can turn it back on.
Recently it started to turn itself off..... and then I have to wait for several hours till I can get it to work again..... any tips on how to solve this?

Imac shuts down 5 seconds into start up. Troubleshooting not working.

Imac shuts down about 5 seconds after starting.

Aubrey2320 wrote:
iMac, purchased last year
If you are still under warranty and/or have AppleCare, call them. Let them deal w/it.
OOW: Take your Mac to your local Apple Store or an AASP. Diagnostic testing is FREE!
Other OOW options:
How to save money on Mac repairs with your credit card’s extended warranty
Troubleshooting not working.
There is nothing anyone here can do as you did not provide any of the steps you've tried to solve your problem. Need details to avoid the been there done that scenarios.

IMAC shuts down unexpected

iMac shuts down after ca. 1 hour - 1hr40 running.
Can't restart afterm have to wait 2 - 3 hrs. before restarting,

After digging through a bunch of different posts, I've come to the conclusion that I had a over heating problem. In fact, the fan stopped running altogether causing it to overheat, then shut down.
The vents on the bottom were completely clogged with compacted dust. It was so bad that I literally picked out chunks of dirt with a toothpick. I was able to clean the fans blades by spraying compressed air thought the top holes.
Now she runs cool as a cucumber but there is still one small problem. The fan does not restart when I manually put her to sleep. I've had to stick a small screwdriver down one of the vents on top to give the fan a little "kick start".
At least the problem is nowhere near as bad as I thought it was.
G4 Imac Mac OS X (10.4.8) 1.25GHz 768mb

IMac shuts down

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