my iMac fans are dumb, run when not needed, and don't when do.

Discussion in 'iMac' started by Draddy, Nov 7, 2009.

  1. Draddy macrumors regular

    Joined:
    Mar 16, 2007
    #1
    Any tips on how to fix this?

    Usually, the CPU fan is stuck at 4500RPMs constantly, CPUs 28°? it runs the fan at 5000RPMs.

    But whenever the CPU is cooking, such as 92°, it won't run at all, but the other two fans will be at full blast.


    Any tips on how to fix this? I took the computer to the apple store 3 times for this issue but every time they "could not recreate the issue". The last time the replaced the fans in the computer, but that didn't fix anything.


    Anything that would point me in the direction of fixing this? It's just melting itself. Alum. iMac.

    Thanks!
     

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  2. d15 macrumors newbie

    Joined:
    Nov 4, 2009
    #2
    How do you tell how hot your computer is, such as by the pic you posted at the bottom?
     
  3. Draddy thread starter macrumors regular

    Joined:
    Mar 16, 2007
    #3
    Yes, and physically to the touch.
     
  4. Tim018 macrumors regular

    Joined:
    May 31, 2009
    #4
    SMC Fan Control

    Smc fan control will give you control over the fans in your imac so that you can speed/slow them manually. Im pretty sure a pram reset might do the trick too, if the programming on the fans have just lost their way.

    http://www.eidac.de/ - smc
     
  5. Draddy thread starter macrumors regular

    Joined:
    Mar 16, 2007
    #5
    I appreciate the tip! I believe that program (if it's the one i've tried in the past) only regulates the minimum fan speed, which will definitely help half the problem.

    but I feel like I should be able to bust the case open and replace temp sensors or something.

    Forgot to mention I do PRAM resets, and leave it unplugged for 15 seconds about once a week, and that puts a band aid on the problem, but it always comes back too quickly.
     
  6. Techhie macrumors 65816

    Techhie

    Joined:
    Dec 7, 2008
    Location:
    The hub of stupidity
    #6
    Have you tried resetting the SMC yet? link This is the chip that controls fan speed (hence the app name SMCfancontrol)

    If that doesn't do anything, my guess is that the thermal sensors on your logic board are whacked out. I don't know if they can be replaced individually on the iMac, or if the logic board itself has to be replaced.
     
  7. Draddy thread starter macrumors regular

    Joined:
    Mar 16, 2007
    #7
    Yep, unplugging for a while helps but doesn't solve unfortunately.
     
  8. MacHamster68 macrumors 68040

    MacHamster68

    Joined:
    Sep 17, 2009
    #8
    i postet it quiet often now , in most cases where fans are doing things different as they should cleaning is the first action to take before messing up the system with all sorts of programs , the fans are there to cool things but if its clocked up with dust they get confused , i regular clean every computer be it pc or mac inside and give the fans a bit wd40 once a year at least and so far not a single failure of a fan in the last 20 years and you may be surprised how much dust they collect inside they are like little hoovers , possibly good for asthmatics but not so good for vital parts of the system
     

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