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  1. #1
    Unplanned Shutdown

    Member Since
    Jun 12, 2011
    Posts
    4
    Question Unplanned Shutdown
    I am having problems with my iMac unexpectedly shutting down. I have had this problem for a while (years) but it has gotten dramatically worse to the point where it is shutting down 3 times within a 10 minute span. I have tried moving the power cord to trigger the shutdown but nothing happens. I have ran programs like istat nano, S.M.A.R.T. Utility and Disk Utility but I am not sure how to correct the errors they might find. I don't know the cause of this problem. I am trying to get a presentation ready for a wedding using iMovie but it is proving difficult when the computer shuts down every 15 minutes. I am out of my Apple Care Warranty and would like to avoid the $50 service fee if possible. I am not sure if it is a overheating issue, hard drive failure issue, or bad RAM. If there is a test, I can run it and post the results as quickly as I can. Here are some basic stats about my iMac

    OS: 10.6.7
    Processor: 2.4 GHz Intel Core 2 Duo
    Memory: 2 GB 667 MHz DDR2 SDRAM
    HD: 100 GB free

    Temperatures (in F) from istat right after a shutdown:
    HD: 126
    CPU: 121
    GPU: 139
    GPU DIODE: 142
    GPU HEATSINK: 139
    AMBIENT: 81
    MEMORY CONTROLLER: 124
    AIRPORT CARD: 148
    HD BAY: 122

  2. #2
    Unplanned Shutdown
    Dysfunction's Avatar
    Member Since
    Mar 17, 2008
    Location
    Tucson, AZ
    Posts
    6,821
    Specs:
    Way... way too many specs to list.
    With those temps I'd pretty much rule out thermal shutdown. Have you tried resetting the SMC?
    mike
    This machine kills fascists
    Got # ? phear the command line!

  3. #3
    Unplanned Shutdown
    powermac G5's Avatar
    Member Since
    Oct 17, 2008
    Location
    Bowmanstown, PA
    Posts
    256
    Specs:
    *27" imac C2D 3.0/1TB/16GB**Mac Pro Octo 2.8/4x1TB/16GB**Mac Pro Quad 2.66/2x1TB/8GB**iPhone 4*
    Replace CMOS. Have seen many that will report erratic issues, even failed CPU diagnostic lights. OSX is not kicking in that "old chestnut" any more that "your time and date are set incorrect" this will cause erratic behavior if not addressed.
    Regards

  4. #4
    Unplanned Shutdown

    Member Since
    Jun 12, 2011
    Posts
    4
    Dysfunction,

    I have tried resetting the SMC and I still have the issue of unexpected shutdowns.

  5. #5
    Unplanned Shutdown

    Member Since
    Jun 12, 2011
    Posts
    4
    Quote Originally Posted by powermac G5 View Post
    Replace CMOS. Have seen many that will report erratic issues, even failed CPU diagnostic lights. OSX is not kicking in that "old chestnut" any more that "your time and date are set incorrect" this will cause erratic behavior if not addressed.
    Regards
    I am assuming that you are referring to the PRAM or logic board battery? I have not had any issues with my time and date being set incorrectly that I am aware of. I was researching the CMOS and it seems that is in the G3 imacs. I was looking at the battery info and it seems that it is linked to the Power Management Unit. I just want to make sure before I open the hood on this intel imac.

  6. #6
    Unplanned Shutdown
    chscag's Avatar
    Member Since
    Jan 23, 2008
    Location
    Fort Worth, Texas
    Posts
    45,202
    Specs:
    27" iMac i5, 3.2 GHz, iPad 3, iPhone 5c, iPhone 6+, 3 iPods, Yosemite
    I doubt seriously it's an issue with the PRAM battery. Unexpected shutdowns are almost always related to hardware. The two things that most likely cause shutdowns as you're having are bad memory or a flaky power supply. It could also be caused by a bad logic board.

    Since the memory is easiest to check, start with that. The power supply is going to require technical ability to trouble shoot and is difficult to access. Any kind of maintenance (other than memory replacement) on an iMac requires that the display panel be removed first.

    It may be best to let an authorized Apple service center do the trouble shooting and repair if it turns out not to be a bad memory module.

  7. #7
    Unplanned Shutdown
    harryb2448's Avatar
    Member Since
    Nov 28, 2007
    Location
    Nambucca Heads Australia
    Posts
    20,020
    Specs:
    iMac i5 2.7GHz, 16GB memory, OS 10.10.5
    And to add to the above post, dust will also cause problems and iMacs are not the easiest to crack and clean.
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

  8. #8
    Unplanned Shutdown

    Member Since
    Jun 12, 2011
    Posts
    4
    Quote Originally Posted by chscag View Post
    I doubt seriously it's an issue with the PRAM battery. Unexpected shutdowns are almost always related to hardware. The two things that most likely cause shutdowns as you're having are bad memory or a flaky power supply. It could also be caused by a bad logic board.

    Since the memory is easiest to check, start with that. The power supply is going to require technical ability to trouble shoot and is difficult to access. Any kind of maintenance (other than memory replacement) on an iMac requires that the display panel be removed first.

    It may be best to let an authorized Apple service center do the trouble shooting and repair if it turns out not to be a bad memory module.
    So I ran memtest tonight and everything passed when I did the single user mode. I rebooted the computer and upon the reboot, it shutdown. I guess it has to be something other than the memory. I assume that there is not a way to test the power supply or the logic board. I have already tried Apple Hardware Test Extended and it said everything was fine.

  9. #9
    Unplanned Shutdown
    powermac G5's Avatar
    Member Since
    Oct 17, 2008
    Location
    Bowmanstown, PA
    Posts
    256
    Specs:
    *27" imac C2D 3.0/1TB/16GB**Mac Pro Octo 2.8/4x1TB/16GB**Mac Pro Quad 2.66/2x1TB/8GB**iPhone 4*
    Quote Originally Posted by chscag View Post
    I doubt seriously it's an issue with the PRAM battery. Unexpected shutdowns are almost always related to hardware. The two things that most likely cause shutdowns as you're having are bad memory or a flaky power supply. It could also be caused by a bad logic board.

    Since the memory is easiest to check, start with that. The power supply is going to require technical ability to trouble shoot and is difficult to access. Any kind of maintenance (other than memory replacement) on an iMac requires that the display panel be removed first.

    It may be best to let an authorized Apple service center do the trouble shooting and repair if it turns out not to be a bad memory module.
    Replace the CMOS/PRAM battery/Back up battery, what you guys call it, you know what I speak of, replace the battery trust me:-)
    I buy pallets of salvage macs and refurbish for resale. This puts food on the table and a roof above and to be perfectly honest I have replaced CMOS batteries in 2006 Mac Pro that report errors with cpu's deemed by apple to have failed logic boards, battery is dying. OS X does NOT pick up everything.
    Tell me have, you seen time and date not set with SL? Your computer will act erratically as 10.5 would show, hence even unexpected shut downs. No matter if a hardware issue you will be opening the mac to inspect, start cheap and replace that silly back up battery that every one neglects.

  10. #10
    Unplanned Shutdown
    powermac G5's Avatar
    Member Since
    Oct 17, 2008
    Location
    Bowmanstown, PA
    Posts
    256
    Specs:
    *27" imac C2D 3.0/1TB/16GB**Mac Pro Octo 2.8/4x1TB/16GB**Mac Pro Quad 2.66/2x1TB/8GB**iPhone 4*
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