PWM splitter

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  • csh
    Member
    • Mar 2015
    • 38
    • Croatia
    #1

    PWM splitter

    MBO in my main rig at home has only 4-pin fan connector, for the CPU fan. The rest are standard 3-pin.
    Recently i got this PWM adapter and two of these fans.
    In theory it should work fine: fans are drawing power from molex and are controled via PWM signal from the MBO that reads rpm from the CPU fan (old Freezer 64 pro).
    But, after powering up, BIOS reads 1800 rpm on the fan and it really spins faster. After stressing the CPU some time it spins gradually up to 2400 rpm which is close to the specified max: freezer has a fan rated for 900-2200 rpm.
    Swapping the places of new fans didn't help. If i leave only one fan connected (any position, tried with both fans), BIOS reads around 1000rpm at cold start and CPU fan slowly spins up to 2400 rpm.
    With only the CPU fan connected it spins from 950-2300 rpm.
    It seems that winth only one additional fan on the splitter the reading is a bit off by 100-200 rpm, but with all 3 fans it works 1800-2400.
    Any ideas why this setup isn't working?
    Tags: None
    • stj
      Great Sage 齊天大聖
      • Dec 2009
      • 30952
      • Albion
      #2
      Re: PWM splitter

      disconnect the tacho pin from one of the fans - they are canceling each other out.

        Comment

        • csh
          Member
          • Mar 2015
          • 38
          • Croatia
          #3
          Re: PWM splitter

          Originally posted by stj
          disconnect the tacho pin from one of the fans - they are canceling each other out.
          There is not tacho (pin 3) on the connectors to the two case fans. they have only pwr,gnd and pwm (pin 4).
          If i disconnect pin4 that fan would spin at full speed and that is what I'm trying to avoid.

            Comment

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