iMac getting hot and fans not speeding up

Discussion in 'iMac' started by chedmaster, Apr 4, 2009.

  1. chedmaster macrumors newbie

    Jan 11, 2009
    Hello everyone.

    I bought my 2.8 GHz Core 2 Duo iMac for a Physics project at university simulating glass formers. As a result, the iMac is running both cores at 100% for days at a time. At the moment it has been running for 4 days at full pelt and the CPU is at 75 C, heatsink at 59 C and ambient at 23 C. These seem fine to me for a Core 2 Duo (my MacBook used to run above 80 C doing the same simulations). The fans never go above 1200 rpm (CPU) 1200 rpm (hard drive) and 700 rpm (optical drive).

    It just worries me that the iMac doesn't seem to care. I'm throwing pretty much everything I can at it and the fans never go above the base 1200 rpm. AFAIK the fans can go to about 6000 rpm.

    - Should they be speeding up at these temperatures or shouldn't I worry?

    - Why can the fans go to ~6000 rpm even if 100% processor usage doesn't require it?

    - I don't like to try SMC fan control etc as I heard they invalidate warranties, is this true?

  2. aki macrumors 6502a

    Mar 2, 2004
    you are right the cpu is meant to take high temperatures.... its probably the hd that is worst in heat

    - it does sound strange to me and

    - yes this is a good point but

    - i use smcfancontrol so i wouldnt know

    i cant see why smcfancontrol would affect any warranty at all but im not a lawyer..... in my case i use smcfancontrol when i do heavy video work 24-hour encodes and stuff or heavy gaming and it works very well for me

    i should say if your imac is being replaced regularly i mean like 2-3 years i dont think youd probably have to think about heat at is well designed for heat given the form factor
  3. kastenbrust macrumors 68030


    Dec 26, 2008
    North Korea
    Please whatever you do dont use SMC Fan Control, use a decent piece of software like Fan Control 1.2 instead:

    SMC belongs in the jurassic era.

    Fan Control 1.2 is variable, so you have a min and max temp and it automatically controls the fans for you, much better than the stupid fixed speed SMC gives you.

    None of these void your warranty.
  4. darrellishere macrumors 6502

    Jul 13, 2007
    Heat killed my original white imac!

    It did the same thing, refuse to crank up the fans when needed until it was too late! Toasted!

    Do you have apple care?

    If so their is no need to worry, as it will be covered if anything goes wrong.

    If not I would definitely be using smc fancontrol, its totally free, safe, and protects your investment, & not void warranty.
    Some one said that it would increase wear on the fans, but that is just an opinion .
  5. txnoob macrumors 6502

    Mar 12, 2009
    I'd rather wear out my fan then fry a cpu. I've used smc with great success, but there are more advanced apps I'm sure.
  6. chedmaster thread starter macrumors newbie

    Jan 11, 2009
    Thanks for all the replies

    I tried Fan Control 2, and it set the default optical fan speed to 1000 rpm which is silly (default before was 700). It won't go below this. So I uninstalled it as per the instructions on the website (reset SMC and PRAM after deleting the daemon and pref pane).

    Now iStat is reporting 0rpm for HDD fan. Can't remember what temperature the HDD was before but it's now 57 C, is the fan broken?! Any ideas on how to recover the sensor reading?

  7. aki macrumors 6502a

    Mar 2, 2004
    i was going to upgrade from the jurassic era but now you scare me.... ?
  8. Blue Sun macrumors 6502a

    Feb 11, 2009
    Doesn't the iMac automatically shut itself down when the temps get too hot?
  9. aki macrumors 6502a

    Mar 2, 2004

    the issue isnt if the imac is going to explode more just of lifespan of components.....well that plus frustration of shutdown midgaming :)

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