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  1. #1
    Member charmapsyche's Avatar
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    Question about changing fan speed...

    I have an 80mm fan that only has the 4 pin molex power and the smaller 3pin fan connector.

    -However, the 3 pin fan connector only has the yellow wire connected to the fan.

    -When I plug the 3pin fan into the motherboard, I can see the RPM of the fan in the bios along with other programs, however I can't change the speed...

    - It seems obvious to me that that's because the black and red(power) wires are not there!

    -I tried the speedfan program and had no luck.

    -Is there a cheap, and preferably simple way to control the speed of this fan? -Or should I just buy a piece of hardware to plug the fan into?

    thanks!

  2. #2
    Member SwooshingRob's Avatar
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    Re: Question about changing fan speed...

    Originally posted by charmapsyche
    -However, the 3 pin fan connector only has the yellow wire connected to the fan.
    Are you really sure there's only one wire connected??? Normally you would need plus and minus to get an electric motor spinning.

    By re-reading your post I understand that your fan gets the power from a four-pin connector and connects to the motherboard via a three-pin connector. If that is the case, the single yellow wire is the speed sensor. (Sorry for being daft. Your posting is quite clear.)

    To be able to adjust the fan speed using software you need to get the power from the 3-pin connector. If you don't want to rewire that you can always put a rheostat or a fan-controlling circuit on the four-pin connector. Have a look at this link for some ideas: http://www.cpemma.co.uk/index.html

    Note that you need to adjust the speed by altering the positive voltage. Ground needs to be ground or the speed sensor won't work.

    Cheers,
    Rob

  3. #3
    Member charmapsyche's Avatar
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    -Well, lets see. I burned up two potentiometers, I do not recommend using potentiometers that have incorrect resistance.

    -However I did end up trying the 12 to 7 volt trick and it worked perfectly!

    -I also boosted my 2500 barton (non-mobile) to a 3200 for now... and I'm still running 10 degrees cooler!

    -When I figure out why my Bios doesn't offer 12 as a multiplier I should be able to get another 200 MHz out of it, but it doesn't seem too stable at 13(aircooled...)

    -Thanks

  4. #4
    Member SwooshingRob's Avatar
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    Bummer. Luckily potentiometers aren't the most expensive components to burn. Glad that you sorted it out with the 7 volt trick though. Apparently that is a very popular mod. The only disadvantage is that you can't adjust the speed. But as long as it delivers adequate cooling at 7 volts there's not much point in adjusting it anyway...

    /Rob

  5. #5
    Member Parkest's Avatar
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    The yellow wire does sense the rpm of the fan on the motherboard, although, this wire doesn't have anything to do with changing the speed. Thats where fan controllers come in. You'll hook up the fan controller, use the adapter to the 4 pin molex to give the fan power, and then regulate the speed by the fan controller.

    here

  6. #6
    Member OKJEFF4's Avatar
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    Well said Parkest. I laughed a lot when I read the first post, but I am sorry now. Good luck.

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