11 Replies Latest reply: Jul 10, 2013 8:30 AM by HunterBD
HunterBD Level 1 (15 points)



I've now read many threads in the Apple Support Communities looking for a list of symptoms likely to be experienced if a hard disk is heading towards total failure, but haven't so far managed to find such a list (just lots of snippets of info!)


If you are aware of where such a comprehensive list may be found, please point me in the right direction.


Secondly, is there some way (other than the Apple Disk Utility) in which I can check my WD drive whist it is still within my iMac? Any advice will be much appreciated.




David B.

iMac, OS X Mountain Lion, +MS Windows 7 on personal laptop
  • John Galt Level 8 (45,943 points)

    You can use Apple Hardware Test. If it reports an error it is certain to exist. If it does not, a problem may still exist but it must be diagnosed by describing its symptoms.


    Other than AHT Disk Utility is the best option. Don't use third party utilities, they often report errors where none are present, and may even cause them to occur.

  • HunterBD Level 1 (15 points)

    Thanks for that information, John!


    This machine came with Leopard and has since been upgraded to Snow Leopard, Lion and now Mountain Lion.


    Will AHT actually be on my iMac now or will I have to go back to the original install disks?


    I'm hesitant about switching off as I'm concerned that it will not start again - I'll likely get a flashing folder containing a question mark!  Then I'll have to unplug from the power supply and leave to cool for half an hour before attempting to restart again!  It's one reason I asked for a list of symptoms!


    Thanks for the warnings regarding third party utilities.



  • John Galt Level 8 (45,943 points)

    Do you believe your Mac is overheating and shutting down on its own? There could be a number of reasons for that. AHT may help find the cause and perhaps provide a clue to what needs to be fixed. Whatever the reason, you should back up your hard disk's contents in the event you can't get it to boot at all. If that becomes impossible, there are still ways of retrieving its contents but the methods become progressively difficult.


    You need to find your original grey Applications Install DVD or whichever one shipped with your Mac that has the words "Apple Hardware Test" or "AHT Version xxx" printed on the disc. Restart your Mac with that disc inserted, while holding the d key. The KB article above explains the procedure.


    A copy of AHT was supposed to be installed on your hard disk when upgrading to Lion, but this failed to install on some Macs that were upgraded to Lion. Loading AHT from the disc is certain to work.

  • HunterBD Level 1 (15 points)

    Thank so much for your help, John! 


    I located my installation discs (2) and opted to use number 1 whilst starting up holding down the 'D' key - und up pops the Hardware Test!  I've never seen that before!


    I ran the quick test and it reported nothing amiss.  So I then ran the 'long' test and was rewarded with the following.


    "Alert. Apple Hardware Test has detected an error".   4HDD/11/40000000:SATA (0,0)


    A quick 'Google' suggests tha's probably not good news!


    Btw, I also have a disc called TechTool Delux - should I run that too?


    I have been using Time Machine to store backups on an external drive!



  • John Galt Level 8 (45,943 points)

    That error indicates a problem with the HD or a problem communicating with it. Consider it good news in that you found it before it fails completely. Check here to be sure you are not affected by the Seagate recall:




    I do not recommend TechTool Deluxe. Broken hard disks can't be fixed. Fortunately they are not unreasonably expensive to replace. The Apple Store can do it, but you can do it yourself if you are sufficiently adept at such things.


    If your hard disk is a Seagate, and you purchased your iMac between October 2009 and July 2011, definitely bring it to the Apple Store even if your serial number shows that yours is unaffected by the recall.


    Back up your hard disk before bringing your iMac anywhere near an Apple Store. Failed hard disks replaced under the recall will not be returned to you.


    Genius Bar Reservations: http://www.apple.com/retail/geniusbar/

  • HunterBD Level 1 (15 points)

    I appreciate all the advice you have given, John - thank you! 


    I was aware of the Seagate scenario - my own HD is a Western Digital. Thanks for mentioning, though.


    I've been reviewing video clips on YouTube which show one how to swap out a hard drive in an iMac.  I'm fairly sure I could have a fair stab at doing it myself but until it's an 'old' machine I'll probably bite the bullit and get a 'professional' to do the job this time!


    WhatI have done is to start my machine from my original Leopard disk and then erase all data from the hard drive. Then I reinstalled Mountain Lion from the Time Machine back-up I have on an external drive. For the mostpart my 'spinning beachball' has now disappeared!  <shakes head>


    One further question if I may.  Do you know where abouts within the machine the Serial Number is stored? (I know how to find it!



  • John Galt Level 8 (45,943 points)

    That's easy enough - click the  menu > About This Mac...


    Click the text - where it says "Version" - right below the bold OS X twice, and your system serial number will appear.


    iFixit.com has detailed pictures and instructions for replacing iMac hard disks. Except for the just released iMac models, removal of the front glass is easy, keeping dust from getting caught behind it is not.

  • HunterBD Level 1 (15 points)

    I can only apologise for not making it clear that I did already know how to 'uncover' the serial number of my machine. What you have described, John, is that exact procedure.


    What I want to know is where - inside my iMac - is the SN stored. Presumably it cannot be on the hard drive as it would be 'lost' if a hard drive is changed.


    Thanks for directing me to http://www.ifixit.com   Very interesting site! 



  • John Galt Level 8 (45,943 points)

    HunterBD wrote:


    What I want to know is where - inside my iMac - is the SN stored. Presumably it cannot be on the hard drive as it would be 'lost' if a hard drive is changed.


    The SN is burned into firmware using a procedure available only to Apple, and yes it will survive a hard disk transplant. It should also match the one etched on the bottom of its stand. There may be other places they don't tell us about.

  • HunterBD Level 1 (15 points)

    How strange that I'd never looked underneath the iMac stand!  Sure enough - there it is!


    Thanks again for all help and advice.

  • HunterBD Level 1 (15 points)



    Please look at this thread:  https://discussions.apple.com/message/22446443#22446443


    All my problems have gone away, now that my hard drive has been changed!  Whoopee!


    Thank you once again for your help, John.