My iMac is shutting down by itself

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My iMac is shutting down by itself

Hello there !

Since a year and a half my iMac is shutting down by itself randomly. Never now when it will occured and why. It just happens. It could be a week and everything works fine and suddenly it shuts down. When I go to the console it says : "05/05/13 08:41:37,000 kernel[0]: Previous Shutdown Cause: -128".

It's an iMac Intel Core i7 2,93 GHz. I've tried a lot of things but anything worked so far. Since I have Apple Care, I've called them and they told me it was the Power Supply. They changed it but it still happens.

I've read throught the Apple Discussions it might be some extra RAM that I had, but I don't really understand how it could shut down the computer... And it's quite impossible to test since it can works fine for one month in a row.

Could it be some extra HD (I've got all the USB used and the Firewire as well) ?

Should I contact Apple Care ?

Thanks for any help !

Posted on May 4, 2013 11:59 PM

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Answer 1

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Paul_31

Level 6

14,160 points

May 5, 2013 12:24 AM in response to mitchmitchel

What version of OS X are you running and how much RAM do you have installed?

There was a monster thread on here a while back regarding random shutdowns of 27" iMacs that were running 16gb of RAM that had been upgraded by users. The end result was that certain brands of RAM were causing the issue. Exchanging the RAM for a different make of chips solved it. I'll see if I can find the thread and post back with a link.

So, if you upgraded the RAM, can you take it out and run, at least temporarily, with just the RAM that came pre-installed with the Mac.

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Answer 2

Paul_31

Level 6

14,160 points

May 5, 2013 12:37 AM in response to Paul_31

Not the thread I had in mind, but same scenario: https://discussions.apple.com/thread/2592483?start=0&tstart=0

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Answer 3

mitchmitchel Author

Level 1

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May 5, 2013 4:21 AM in response to Paul_31

Hello Paul

I have 2x2 Go (preinstalled) and 2x4 Go from Crucial. I have read the massive thread, and well it works for some people and not to others... I will try however. However some people say that it's a fan issue (the iMac gets too hot), but I was pretty sure the "previous shutdown cause" will be different that 128 which is, according to a Genius I had on the phone, is a power failure (so the RAM shouldn't be involve, but not too sure)...

Thanks...

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Answer 4

Paul_31

Level 6

14,160 points

May 5, 2013 4:58 AM in response to mitchmitchel

If you haven't got it already, there's a useful free widget for monitoring temperatures, fan speed and a bunch of other stuff - istatpro: http://download.cnet.com/iStat-pro/3000-12565_4-71074.html

You may do this already, but something worth doing on a regular basis to help prevent overheating is to vacuum out the vents (with the Mac turned off). I've got the previous generation iMac and do the vents along the bottom where the speakers and RAM are, the circular fan behind the stand and the extract vent along the top at the back. And, for good measure, I do the CD/DVD/SD card slots on the side 🙂.

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Answer 5

Lexiepex

Level 6

14,102 points

May 5, 2013 5:53 AM in response to mitchmitchel

Certainly not the "fan" cause: you will hear that coming clearly when the fans get up to 6000 RPM.

I agree with Paul: almost certain a ram issue, although Crucial is a very good brand: are you sure the new ram has exactly the same spec as the original ram?

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Answer 6

WZZZ

Level 6

13,226 points

May 5, 2013 6:04 AM in response to Paul_31

A bit OT, but I recently had my screen replaced by an on-site tech. Despite my conscientiously vacuuming all those all the time, he blew out a ton of dust from all three fans. I guess it could have been worse if I hadn't.

userCanceledErr

= -128,

Also, don't understand the connection between possibly questionable RAM and overheating.

Message was edited by: WZZZ

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Answer 7

mitchmitchel Author

Level 1

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May 5, 2013 6:58 AM in response to mitchmitchel

Well thanks for your help. I will try the RAM issue.

LexSchellings > I used their tool to determine which RAM I should buy. I've got TechTool Pro and for this application, the RAM is "good". I'm quite suprised that a RAM issue can shut down the computer. I bought once noname RAM for a MacBook and I had kernel panic all the time, much more you can expect for a disfunctionnal RAM.

So far, I reset the SMC. And I'll wait the next "express shut down" to try without my Crucial RAM...

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Answer 8

Lexiepex

Level 6

14,102 points

May 5, 2013 7:16 AM in response to mitchmitchel

It may happen, even when the specs are OK, I agree that their configurator to search the right spec is good, I have Crucial Ram myself. Maybe reseating is enough. Before going to Apple care try if you have the same unexpected shutdown behaviour with the original Ram.

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Answer 9

Linc Davis

Level 10

209,547 points

May 5, 2013 8:51 AM in response to mitchmitchel

Have you reset the SMC?

Is the machine connected to an UPS?

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