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My 27" Imac (A1312/EMC2390) keeps shutting down...

My 27" Imac (A1312/EMC2390) keeps shutting down unexpectedly with no warning or "screen of death". So far I reset the SMC, and zapped the PRAM. I even replaced the power supply but the problem continues. My error and system logs seem unhelpful too. Can anyone help me out?

Do you still have AppleCare?

Sorry, but I do not.

I should have added to the original post that I had also tried a clean install of the OS. (10.6.8)

Was the power supply replaced under AppleCare or did you replace this yourself?

And are you sure this was the correct power supply for your model iMac?

Trying to elimate hardware issues.

Also, have you tried to disconnect your iMac completely from power for 5-10 mins and allow it to reset itself?

I replaced it myself, today. It first shut down within 3 minutes of starting up after the replacement, then a couple more times since then. All the part numbers on the power supply are the same as the original one, which I suspect was fine all along. So its the same issue, with 2 different power supplies.

Right now its been turned on for about 3 hours without a problem. Its just sitting there though, and I'm using other computers for now. I'm going to leave it on overnight and see what happens.

You can get a shutdown like that if the computer gets too hot. Make sure the air intakes on the bottom and the exhaust vent on the top are clean and are not blocked by something in your workspace like papers or the back of the computer being too close to part of the furniture. You need a good six inches (15cm) of clearance between the exhaust slot and other objects or surfaces.

Anti-virus/internet security software, especially the "pay for" kinds, can increase operating temps. So can third-party backup software furnished with many "name-brand" external hard drives.

Fan motors and/or temperature sensors can fail. If you have the original grey disks that shipped with your iMac, find the on that has Apple Hardware Test (AHT) and run it. If you have a failed heat sensor or fan motor, it will detect it with an error code containing "SNS" if it's a bad sensor or "MOT" if its a bad fan motor.

AHT instructions here:

https://support.apple.com/kb/HT1509

Also see if your iMac 27 falls under theis Apple Repair Extension Program:

iMac 1TB Seagate Hard Drive Replacement Program

This has been going on for months now. Sometimes its good for several days in a row. .Its been turned off and unplugged for days at a time. Most recently while waiting for the power supply to be delivered

Did you install OS X Snow Leopard from the original restore discs that came with the iMac?

Get iStat Pro widget, which will display temps and fan speeds. Post the temps in Celsius please, but only after it's been up for a while running with the programs that are open when the shutdowns occur.

https://www.macupdate.com/app/mac/20364/istat-pro

Its not the temperature. The fans are working, and clean. Today it failed within 3 minutes of its first startup in the morning. And there's no blockage of air circulation around it.

Also, there's no antiviral programs in use on it as that's handled by our corporate firewall.

I'm running the Apple Hardware Test right now. Should have thought of that one myself. Thanks.

I Would do as Allan has suggested.

Some real,good advice there.

It's possible you might have missed something when you did the take down or reassembly of the iMac?

As experienced as I am working on Macs, the newer aluminum model iMacs are not designed to be easy to work on and upgrade/replace things and you need to have real patient and really pay attention to all of the little details, screws, clips and wired connections when working on these iMac models. It's too tedious and nerve wracking work that I won't ever try to undertake.

AHT says "No trouble found". Not unexpected on such an intermittent issue.

And yes, I used the original installation disks for both the clean install, and the AHT test.

What are you showing for fan speeds?

最後更新：2017-09-24 09:44:33

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