How to control the Max temp of fans, and booting off an external HDD

Discussion in 'iMac' started by Isometric Bacon, Nov 19, 2010.

  1. Isometric Bacon macrumors newbie

    Nov 19, 2010

    I have a 2007 Intel 24" iMac (Last of the white plastic editions) and i've recently had troubles with the 7600GT Graphics card. The computer would get strange artifacts all over the screen, before crashing.

    Unfortunately, it is out of Applecare, so I took it into a shop and had the card replaced.

    Upon receiving it back, they told me that they replaced the graphics card, but still found problems with it booting up inconsistently. After some testing, they realised it was the Hard Drive controller at fault, and put my harddrive in an external USB enclosure and booted it off that instead. This was an easier solution than replacing the entire logic board, they told me. (and they gave me the enclosure for free).

    Now i've brought it home, and set it all up, only to find that the HDD fans are CONSTANTLY spinning at 5600 RPM, which is deafeningly loud, even so over my room fan. I presume this is because there is no longer any hard drive controller/hard drive in there.

    I've installed SMC Fan Control, but to my dismay you can only set the minimum fan speed, and not the max. If possible, i'd like to set the max fan speed at a much lower rate, without needing to open up the iMac.

    So my questions are:

    Is there a way I can set the max fanspeed for the HDD, or disable it since there isn't one in there anyway?

    And is there a better solution for booting my iMac OS onto an external HDD? (i.e. Should I look into buying a firewire 800 drive enclosure instead of this USB 2.0 one?)

    Many thanks.
  2. Isometric Bacon thread starter macrumors newbie

    Nov 19, 2010
    As a partial update, i've found a few terminal commands that limit the fan speed in SMCControl - but it appears to only be doing it for the CPU fans, and not the HDD Fan :(
  3. Tempto macrumors member

    Oct 24, 2010
    I am also looking for a way to reduce the max fan speed on the HDD. Input would be appreciated!
  4. MacHamster68, Nov 20, 2010
    Last edited: Nov 20, 2010

    MacHamster68 macrumors 68040


    Sep 17, 2009
    to the op , i guess you need to attach the thermo sensor , sounds like they forgot it when they took out the harddrive, so playing with smc settings is pointless unless you check the sensor is attached first
  5. rekhyt macrumors 65816

    Jun 20, 2008
    Part of the old MR guard.
    Completely unnecessary. Surprised, it hasn't been mentioned, but:

    Fan Control. (

    You can set the upper limits and lower limits of the fan control, when the fan kicks in, ...

    Immensely helpful and much better than SMC Fan Control.
  6. MacHamster68, Nov 20, 2010
    Last edited: Nov 20, 2010

    MacHamster68 macrumors 68040


    Sep 17, 2009
    i still believe, that at apple are working some intelligent chaps who know what they are doing and what settings for the iMac's fans are best , but i could be wrong and at apple some chaps decide the settings by rolling some dice as they go along ,
    but with so many crying out for other smc settings because they think more then the average persons body temperature is way to high for a iMac's CPU or GPU , the later could be true and the chaps at apple really have not a clue about how to set fan speeds :confused:
  7. Isometric Bacon thread starter macrumors newbie

    Nov 19, 2010
    Thanks. Unfortunately there are no Apple Stores in the city I live (Adelaide, Australia), and I instead need to go through Apple authorised resellers... My experiences have very much been a mixed bag.

    I was very happy with the price, attitude and service given by the shop I had these repairs done... (They're certainly better than other mac resellers i've dealt with) but in the end the problem isn't really fixed. The fan is just too loud for any means of productive work, and booting off a USB drive means that the computer is far too slow for my work needs (Graphic Designer).

    I'm thinking of taking it back and asking if they can double check to see if the temperature plug is in. Either that, or I'm going to open it up and have a try myself.

    Does anyone know of any decent guides to pulling apart the white 24" Intel iMac's and where I should look specifically for the temperature sensor control?

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