Case fan splitter help

[petersonjd1627]

I have PWM 4pin case fans and would like to purchase a splitter due to not having enough MOBO headers. It seams the more common splitters have a 4pin (MOBO connection) and split to one 3pin and one 4pin connector. Is that normal? will both fans still work as PWM?

 

[Aeacus]

4-pin fan won't work in PWM mode if the splitter is 3-pin. However, it does work in DC mode.

For proper Y-splitter, you can go for Noctua ones,
amazon: https://www.amazon.com/Noctua-NA-SYC1-Accessory-4-pin-Y-Cables/dp/B00KG8K5CY
(2x in the box)

 

[petersonjd1627]

That's the crazy thing. I have a Noctua fan splitter and it splits to one 4pin and one 3pin. This is what led me to the question. Ultimately I would like all fans connected to the same MOBO header running at the same speeds. Here is a picture of the splitter i have:

https://www.dropbox.com/s/z8pr4aeexzws6bw/IMG_20181026_163359.jpg?dl=0

 

[Aeacus]

Since your Y-splitter misses the 3rd pin (which would feed fan RPM data back to MoBo) and not the 4th pin (for PWM signal), 4-pin fan plugged to it still operates in PWM mode.

The fan pinout is as follows:
pin #1 - +12V
pin #2 - ground
pin #3 - sense (RPM feed back to the MoBo)
pin #4 - PWM (PWM control for 4-pin fans)

Because MoBo header can read only 1x fan RPM data, the 3rd pin is not needed in 2nd connector and thus is removed.

 

[petersonjd1627]

That is exactly the information I was looking for. THANK YOU!