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Connect 4 wire fans in parallel

Discussion in 'General Hardware' started by greenhouse, Jan 22, 2009.

  1. greenhouse New Member

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    My 3 wire case fan is always running at high speed and is very noisy while my cpu fan is nice and quiet.

    Can I connect two 4 wire fans to the motherboad fan connector in parallel?

    Later edit:
    I have replaced the 3 wire case fan with a four wire one.
    Last edited: Jan 22, 2009
  2. MRCL

    MRCL

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    You mean, operate two fans on one motherboard plug, am I correct?
  3. PVTCaboose1337

    PVTCaboose1337 Graphical Hacker

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    Are you replacing the noisy one with two less noisy ones? I don't understand.

    But yes, as long as the fans are not really amp hungry, you should be fine putting them in parallel.
  4. greenhouse New Member

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    Yes, you are correct MRCL.
  5. Zanga New Member

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    4 pin coolers are PWM (Pulse-width modulation) controlled. You cant connect two coolers together as the speed signal / phase and the pulse speed control will mix, thus making the both spin to fast, nor at all, or damage the MB controller.


    Later edit:

    You can still solve the problem. PWM coolers without sense and control spin at the maximum rpm given by it's power supply. On the case fan remove the speed sense and pwm control wire and leave only the power supply and ground. The MB controller will "see" only the cpu cooler and control it's speed, but you tied the second cooler to it, so both coolers will run at controlled speed.

    You still should check whats the maximum current allowed by the MB and whats the maximum combined power draw of the two coolers.

    Later edit 2:

    Pin Function & Wire Color
    1 GND Black
    2 12 V Yellow
    3 Sense Green
    4 Control Blue
    Last edited: Jan 22, 2009
    greenhouse says thanks.
  6. AsRock

    AsRock TPU addict

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    Plug the 3 pin fan in to another 3 pin connector on the mobo also check in the bios for some kind of control for the fan.

    Not all fan connections have the option to control them. Try checking your manual.
  7. greenhouse New Member

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    Excellent response Zanga. Thanks.

    If I understand you correctly, on the second fan I connect only pins 1 & 2.
  8. Zanga New Member

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    Yes correct, use only pin 1 and 2 and connect them to the same wires on the CPU cooler, but check first what's the current rating of the fans.
  9. greenhouse New Member

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    Hi Zanga.

    I just tried it connecting only pins 1 & 2. One or both of the fans went to high speed.
    Same result connecting pins 1, 2, & 3.

    What did seem to work was connecting pins 1, 2, & 4 and leaving pin 3 unconnected on the case fan.
    Last edited: Jan 22, 2009
    Zanga says thanks.
  10. Zanga New Member

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    :banghead: Just forgot that the power supply stays constant @ 12V. Having the sense off is ok. Now both fans receive 12V, Cpu fan reports speed and MB signals to both to adjust speed. :toast:
  11. greenhouse New Member

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    OK. Thanks. Nice and quiet now.

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