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Late 2012 (27") (i5) iMac

Late 2012 (27") (i5) iMac - Keeps shutting down!

For the past three weeks I have experience my iMac shutting down for no apparent reasons.

Firstly I though it was simply a blown fuse which I replaced.

The problem has become more occurrent over the past week.

I even down graded to Mountain Lion to see if maybe it was the OS or software related, but the same thing happened.

I've since reinstalled El Capitan from a clean install, and still the problem persists.

• I have removed the cable from behind the screen to reset the SMC (Which only helps temporary, but eventually  knocks off again)
• I have tried a clean install of the OS
• I have switched around the Ram sicks
• I have reset the PRAM

there are time were the computer will stay on longer and times when it will only boot as far as the login screen then shut down.

Please could someone help me shed some light on this very frustrating issue....... And the thing is, this computer has been very rarely used since purchase.

Cheers!

Firebrand

A clean install should take software out of the picture. Have you run Apple Hardware Test

Apple Hardware  Test:

https://support.apple.com/en-us/HT201257

It's not very reliable at finding errors but if it does report an error, it can be useful.

Yes I forgot to add that to my list of things I've tried, which I'll do now if i can edit the post.

The hardware test results all displayed everything as ok

Thank you

Yes, as I said AHT is not the greatest for diagnosing disk problems.

And you've run Disk Utility > First Aid on the disk?

Disconnected all peripherals?

Here's the Apple Support Topic on the subject.

OS X: When your computer spontaneously restarts or displays "Your computer restarted because of a problem." - Apple Supp…

Yes tried all of the above to no avail

Will read the link you provided shortly..

Very Much appreciated!

Firebrand

If that doesn't help, take it any Apple Store for a free evaluation. They have far better ways to diagnose hardware problems.

EDIT: Oh, I forgot to mention that if the Mac hasn't been used in a while it could be the pram battery. You might try replacing it.

Wait until the Mac shuts down unexpectedly, then examine your system.log file to identify the numeric code associated with the shutdown. Read below.

Find the Console app - it is in your Utilities folder and looks like this

You can find it by selecting Utilities from the Finder's Go menu.

Open Console.

If the log list column on the left is not already displayed, show the log list by selecting Show Log List from Console's View menu.

Locate system.log in the list and select it. Many date and time-stamped entries will appear, hundreds of them, and you must find the entries relevant to your Mac's problem.

To do that type the words shutdown cause in the Filter field at the upper right of the Console window.

That will cause all log entries to be hidden, except for the entries containing those words. There will be a numeric code associated with the log entry starting with "Previous shutdown cause". What is that code?

Thank you

I typed 'shutdown cause' and this appeared:

Jul 14 00:49:22 Bills-iMac kernel[0]: Previous shutdown cause: 0

Any clue what this means?

Cheers!

Yes. Although Apple does not reveal each code's exact meaning, I have learned from observation that Previous shutdown cause: 0 will always appear if a desktop Mac's power is suddenly interrupted. I have never seen it associated with anything other than that. From those observations it is reasonable to infer the reason for the shutdowns is a power interruption, and not something that can be fixed with software.

The reason for the power interruption can be external to the Mac, such as a defective power cord, wall socket, or poor power quality in your home or electric utility. You can eliminate those potential causes by substituting a different power cord and / or a quality UPS.

Possible internal causes could be an intermittent connection or similar fault anywhere in its power supply circuit, which includes the path from the iMac power receptacle, to the power supply itself, to low voltage paths throughout its logic board and all the connections within. Those causes become much more difficult to troubleshoot.

If you are not successful using a different power cord and UPS then schedule an appointment to have Apple evaluate your iMac. The nature of intermittent problems is such that the likelihood of a prompt and accurate diagnosis is slim. Describe the problem in as much detail as you can, but be prepared for them to immediately conclude there is nothing wrong with it. If they do, insist they keep it for a while longer.

I hate to give you bad news, but your concerns bear a striking resemblance to this Discussion: Re: Re: Re: iMac shuts down randomly for no apparent reason. It involves an iMac model nearly identical to yours. Whether that problem was ultimately resolved or not is unknown, but please read my reply dated Nov 29, 2015 replying to mikestan56. It is on the last page, and might point to a possible solution for you. If you decide to read the entire Discussion beware that it contains lot of irrelevant and distracting crosstalk.

Please follow up with your determinations.

I have re-located the iMac in the home to three different sockets ... The iMac still cuts out

However, after doing a quick Google search regarding the kernel[0]: Previous shutdown cause: 0  Code, apparently it could be faulty ram sticks. I do know that I had installed an app called Memory cleaner around the time the iMac started playing up, but not sure if this is just a coincidence.  

Cheers for the help so far, Its very much appreciated!

Firebrand

Firebrandnire wrote:

... I do know that I had installed an app called Memory cleaner around the time the iMac started playing up,

Get rid of it.

Excerpted from Effective defenses against malware and other threats:

• Never install any product that claims to "clean up", "speed up", "optimize", "boost" or "accelerate" your Mac; to "wash" it, "tune" it, or to make it "shiny". Those claims are absurd.
  • Such products are very aggressively marketed. They are all scams.
  • They generally operate on the flawed premise that a Mac accumulates "junk" that needs to be routinely "cleaned out" for optimum performance.
  • Trial versions of those programs are successful because they provide the instant gratification of greater free disk space.
  • That increased space is the result of irreversible destruction of files, programs, or operating system components normally protected from inadvertent alteration or deletion. The eventual result will be unreliable operation, poor performance and random crashes that may not become evident for months or even years after their use, when updates to programs or OS X are eventually released.
  • Memory "cleaners" that circumvent OS X's memory management algorithms work by purging inactive memory contents to mass storage, which can only result in degraded performance and accelerated hardware failure.

I just performed an extended Apple hardware test and Oh the irony! it said it found no fault, so I proceeded to shut the mac via the test screen but it wouldn't restart I had to perform a SMC with power cable.

I also observed that when the mac shuts down too quickly, that is, the screen goes black immediately and there is no sign of it shutting down correctly, I know it's not going to start up unless i perform an SMC reset.

Do you recon the Memory Cleaner app may be a possible cause to the problems I've encountered?

Cheers again!

Firebrand

Currently reading this very interesting:

https://www.howtogeek.com/171424/why-memory-optimizers-and-ram-boosters-are-worse -than-useless/

Apple Hardware Test is of limited use and won't help at all if the problem is intermittent. The best it can do is identify obviously inoperative hardware.

Do you recon the Memory Cleaner app may be a possible cause to the problems I've encountered?

Not really, but as I wrote such things cannot possibly convey any benefit, will only result in degraded performance, and can certainly contribute to or accelerate inevitable hardware failure. Its presence is a distraction that will complicate troubleshooting.

OS X's memory management differs in fundamental ways from Windows. Apple's proprietary algorithms are considerably more advanced, so some of that article's recommendations are not applicable to OS X. "Worse than useless" is an accurate description though, including categorizing PC "cleaning" apps as scams. This is exactly what I have been saying. The undeniable popularity of such garbage attests to the gullibility of consumers.

最後更新：2017-10-04 15:08:03

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