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PWM Fan in Sawtooth G4?

363 Views 6 Replies Latest reply: Nov 18, 2012 9:10 AM by RogueArtist RSS
RogueArtist Calculating status...
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Nov 15, 2012 6:37 PM


I'm new to the support communities, but have visited here often and have gleaned tons of great information over the years.  Thanks for sharing all the great knowledge!  I'm hoping someone may have insight into the possibility of using a PWM case fan in a Sawtooth G4.  Japamac's website was very helpful in determing appropriate power supply and fan replacements, but I'm confused when in comes to fan connectors, variable speed fans, fan controllers, etc.  The original fan I would like to replace has a small green "sensor" on it that I believe regulates the fan speed.  Can a PWM fan be used for this same purpose?  From what I've read, a PWM fan requires a connection on the logic board, which I don't think the Sawtooth has.  Are new fans being made that have the green "sensor" like the original?  My hope is to find a new fan that will speed up / slow down automatically.  Thanks in advance for any advice!

Mac OS X (10.5.8), 450 MHz Sawtooth G4
  • japamac Level 7 Level 7 (24,390 points)
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    Nov 16, 2012 5:31 AM (in response to RogueArtist)

    PWM fans need logic board connection and PWM aware boards to function in the true sense.

    Voltage control by the logic board and OS kexts can be accomplished using two wires for a 12v connection method.

    True PWM control is not possible without a special controller, but the fans can still function as a normal fan


    If you are replacing a thermally controlled fan (small green sensor), another thermally controlled fan might be better.

    In the PSU, other sensors allow the PSU to control voltage to the fans, so variable speed capable fans can be used (with or without thermal sensor).


    Which fan are you wanting to replace?

  • Dave Hamilton Level 5 Level 5 (6,795 points)
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    Nov 17, 2012 11:46 PM (in response to RogueArtist)
  • japamac Level 7 Level 7 (24,390 points)
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    Nov 18, 2012 1:47 AM (in response to Dave Hamilton)

    Nice fan. Plenty of airflow, good pressure.

    How's the noise compare?

  • Dave Hamilton Level 5 Level 5 (6,795 points)
    Currently Being Moderated
    Nov 18, 2012 8:40 AM (in response to japamac)

    It was about the same as the stock fan, which was running fine at the time. I just wanted more airflow.

    The  position of its heat sensor (clockwise) was important. It needed to match the stock fan. I had neglected to do that at first, and had to reinstall it.


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