Can I plug a 4 pin fan to a 3 pin header?

If I were to use a Rosewill Model RCW-FPS-401 12" PWM Splitter to split a 4 pin header in my motheboard to three 3 pin headers, would I still be able to take advantage of Pulse-width modulation?

1 Answer 1


Apparently a 3-pin fan can plug directly into a 4-pin socket.

Two of the pins provide power to the fan, the 3rd provides an RPM pulse to the motherboard to read the speed. The 4th pin is for PWM speed control.

This link provides some detail: http://www.tomshardware.com/forum/340825-28-case-fans-4pin-3pin-molex

In the case of a 3-pin fan. Speed is controlled by changing the fan voltage. If you plug a 4 pin fan into a 3 pin socket, the fan speed will be controlled by voltage and it'll still work. The plugs are keyed so you can't get the pins around the wrong way.

  • 3
    what I wanted to know was the opposite: can you plug a 4-pin fan to a 3-pin socket? Apr 9, 2013 at 4:25
  • 1
    see my updated answer. yes it should work without any adaptors.
    – hookenz
    Apr 9, 2013 at 5:12
  • @Matt H, thanks for the link! I really liked this part Case Fans: 4pin, 3pin, Molex -- explanation. Mar 3, 2020 at 11:29

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