Model A1225 / Early 2009 / 2.66, 2.93, or 3.06 GHz Core 2 Duo processor

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iMac 24 keeps shutting down

Hi, have had this problem for a while now, the imac just shuts off like the power was cut. Just wanted to know how to find the problem as I would prefer to fix it myself if possible. Have looked in the console but no power issues.

Thanks for your help

Gerry

Update (02/20/2016)

All the lights on etc. When I unlatch lcd light goes off. Can't understand why it just shuts down. Don't wanna buy a psu if it something else plus don't wanna pay for unnecessary repairs if I can do it myself

Update (02/24/2016)

Still going off. All the led lights are on when supposed to be. Can stay on for a long time then go into sleep mode but when I start an app it goes off. Help with this would be greatly appreciated. Is there somewhere in the log where I would find out the problem?

Update (03/03/2016)

It's a last shutdown cause the code number. I haven't a clue what to try now. Took the logic board out yesterday. No dust on Gan or in the vents of the logic board

Update (03/04/2016)

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Update (03/04/2016)

Me again. Just did the full extended hardware test. No problem. Reinstalling el capitan at the moment. If my HD is dead would it still shut down while running off external drive. How do I check if fan behind. Logic board is running since I have to take it out to see. I think I might just have to give up and put some money away to buy another Mac

Answered! View the answer I have this problem too

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PS it doesn't shut down in safe mode

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Boot up from your original system installation DVD to see if this is possible software issue. Next boot from the DVD holding down the "D" key and run diagnostics.

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Ok I'll give it a try if the cd drive doesn't spit it out

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I think you'll need to get someone local to help you here. Things are just not adding up. If you can go into Safe Mode with no problems that would imply you have a HD or OS level issue. But you also state a known good external bootable drive or OS CD/DVD won't work either.

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Install the app I pointed you to in my first answer TG Pro

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Most likely you have a temp issue. Have you opened the system up and cleaned it yet? I would start there.

I would also recommend you install a sensor monitoring app like this one: TG Pro. If you buy the full version it will log the fans & temps upto the point of the system shutting down. So you can see if that is the issue. Paste a screen shot of the TG Pro console so we can see as well.

Update (02/19/2016)

If the system looks clean and the sensors all look good, it's starting to sound like a power supply problem.

What does the diagnostic LED's doing? Now that you have the display off.

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hi, thanks for the reply, did what you said, opened itn not dusty or dirty, installed tg pro, last shutdown...automatic unknown cause, temperatures sensors seem to be working normally, fans normal also

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Hi. Just installed is on external hard drive but to no avail. It still shuts down. Shutdown cause -128 in console every time. I would really appreciate help in this. Took the whole thing apart. Very clean inside. No dust whatsoever. Any help would be appreciated. Gerry

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Do what Dan says first. The no dust at all comment bothers me. These things are vacuum cleaners and suck dirt in. The shut down may be caused by automatic shut down from high temperatures caused by a failed fan or temperature sensor not kicking the fans on. There are generally three fans, a CPU an behind the logic board, an optical bay fan on the right and a general fan on the lower left side. See if you can determine if all are kicking on.

Are you force quitting programs?

A -128 shutdown code indicates a hardware-related shutdown of unknown cause.

error -128 userCanceledErr User canceled an operation http://www.cs.cmu.edu/afs/cs/user/lenzo/...

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I actually reinstalled old 2009 osx version it held out well but did actually shutdown the same way with the same shutdown cause - 128. Doing extended hardware test with disk at the moment. The fast test didn't find any problems

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Just a question. I see all the two fans working but how can I check the one under logic board to see if it runs while on??

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You could unplug the two outer fans and listen.

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The same is happening to me. As Murphy I tried everything but nothing worked for me. One important point is that on safe mode it doesn't happen.

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I also have the exact same problem, and gave up on it since it cost too much to replace, so I'm throwing this here in case it can be of some use to others, I narrow it down to these:

boot up OSX in safe mode = running fine

installed Windows on it with VGA driver (NVIDIA's) = instant shutdown

remove said VGA driver from Windows = running fine

so I guess it have something to do with VGA card, or the power supply can't handle VGA in full power

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Reapply thermal paste on CPU solved this problem for me.

greetings, Rob van Vroenhoven / Yormac

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gerard murphy will be eternally grateful.
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