Imac 24 overheating. Repair question

Discussion in 'iMac' started by guytam, Jun 25, 2012.

  1. guytam macrumors newbie

    Jun 20, 2012
    I have iMac 24 intel due core 3.06 4 gb ram nvidia 8800gs 2008.
    The problem is that it's started to overheat get to 120c and shutting down.
    The fastet way it gets to shutting down is when I watch video on browser, less then a minute, i can watch video on vlc for hours and it will not pass the 80c.
    Also when using 3d it gets a bit hot but usually don't get 120 unless it's start beach balling...

    I took it to a authorized lab and at the first test they couldn't see any problem
    After that they clean everything and ran the apple test and they saw that the hd fan is slow in 600rpm, and they told me that it probably the problem.
    Before I took it to the lab I backed up using time machine and it didn't
    Got overheated or something 80c, now they called and told me its the logic board, because the sm something test says about sensor problems.
    And I need to replace the board, the thing is that I'm not sure about they reliability, because every one I know that went there needed to replace the logic board, I just want to know if it make sense... And if there is something I can do to confirm it. Any ideas will be great.

  2. 141n5 macrumors member

    Mar 11, 2012
  3. guytam thread starter macrumors newbie

    Jun 20, 2012

    Yes I first thing I bought when the problem started.
  4. joe-h2o macrumors 6502a

    Jun 24, 2012
    Assuming that all the sensors are working properly, I would start to suspect poor thermal conduction between the cpu/gpu and their respective heat sinks. Perhaps the thermal paste has cracked, or the heat sinks have come very slightly unseated from one or other of those chips.

    If the iMac has been serviced at any point this is a possibility. Before you commit to a full logic board change (I assume it's not under warranty) maybe try removing the heatsinks and reseating them with new thermal paste.

    If the temp sensors are measuring near the heat sink itself (I do not know - I've not personally taken a 24" apart) then poor heat transfer could be tricking the iMac into believing the temps are lower, right up until the point it shuts down due to overtemp.
  5. Dadioh macrumors 65816


    Feb 3, 2010
    Canada Eh?
    Possibly thermal paste related or failing fan. I personally don't like the default fan speeds that Apple chooses. I understand they want a quiet machine but I run my fans at min 1500 RPM on my iMac 27" and average temps are about 10C cooler.

    I run iMac Fan Control (free) and adjust the fan profiles for 1500 min speed, ramp at 50C and end ramp at 65C. I personally can't tell the difference in audio level between default fans and 1500 rpm fans but maybe my family room is too noisy :)

    If you get your iMac back from the shop try installing the fan control SW and see if running the fans on a more aggressive profile helps you out.
  6. guytam thread starter macrumors newbie

    Jun 20, 2012
    I decided I'm not gonna fix it in this insain logic board price
    But I'm gonna buy new mbp and wait until new iMacs out and I'll buy one.
    For now, I can't work with the 15" but I do need a laptop
    My question is if it's possible to convert the iMac to a dummy only for the display?
    Without the unneeded hardware ?
  7. Dadioh macrumors 65816


    Feb 3, 2010
    Canada Eh?
    As far as I know only the 27" models can be used as a display by connecting to their mini display port connector. There is no easy way to make yours a display. I would suggest selling it as-is and using the funds to buy a monitor.
  8. guytam thread starter macrumors newbie

    Jun 20, 2012
    You right, i just figure that out.
    i will get the macbook pro with display.

    Thanks for the replies.
  9. Johnf1285 macrumors 6502a


    Dec 25, 2010
    New Jersey
    You could sell the iMac for parts on eBay and still make some money toward your new purchase!
  10. stevenb macrumors member

    Aug 25, 2008
    If you need to buy something to get you buy, look into an Apple refurbished unit. I just picked up a 21.5" iMac for $999.00 and saved $200, which bought AppleCare and 4GB of RAM (2GB x 2). If you need a bigger screen than a 15", maybe try a 17" MacBook Pro. Those are going to get scarce as they are not making them anymore. I had some overheating issues with my 17" MacBook pro as well as a hard drive issue. I took it apart and replaced the heat sink, thermal paste, both fans and a hard drive in a few hours and a couple hundred dollars in parts. Work perfectly with a 750GB hard drive. Temps went down about 25 degree's, but it was not getting as hot as yours.
  11. natx21 macrumors newbie

    Jul 25, 2012
    Imac 24 " xtreme heat

    After 1 year of troubleshootings, this is what i did, instead of replacing the computer.

    Note, temp are in Celsius.

    I hope it will help you.

  12. CheBella macrumors newbie

    I've been trying a 6" fan (made for humans) in the back; it helps a tad, but nowhere near enough.
    While I never had a prob fiddling with the innards of PCs in big roomy cases, I am scared silly to open up the Pandora's box that is the inside of this 24" iMac.
    Here's my Big Plan:
    1) Thermo-pasting a 100mm (4") square sheet of copper to the back of the box where she seems most hot;
    2) T-pasting a heat sink over the copper and;
    3) using my little fan, directed at the heat sink.

    Does anybody thin this would work? Or even help some more?
    Any changes you would make?
    [btw, I downloaded the fan Controller & can't even get it to open, so that's a non-starter.]

    I would appreciate any tidbits thrown my way.

    Thanks in advance!

  13. WhiteNoiseMaker macrumors regular


    Apr 22, 2007
    My 2008 24" iMac has developed the same problem (i think). If the machine gets too hot the screen goes black. The screen will not switch on again after a restart, until the machine has cooled down. The system still boots and can be accessed via my network and the logic board lights are suggesting its just a GPU problem.

    So I might try baking the GPU card for 10 mins in the oven. Then reapplying thermal paste and pads to the CPU and GPU. Hopefully my delivery of thermal paste and pads will come tomorrow so I can complete this over the weekend.

    Hopefully this will fix the problem as everything else is working fine, and I can do without the expense of buying a new iMac. I'll let you know how it goes.
  14. WhiteNoiseMaker macrumors regular


    Apr 22, 2007
    Fixed the problem by baking the graphics card twice for 10 mins at 200ºC. No more blank screen but another problem has developed the CPU fan runs at full blast. I'm using a fan control app until i can find a fix that problem, I suspect its a failed sensor wire.

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13 June 25, 2012