Question 3 pin and 4 pin fan in one splitter?

[refmon]

Hello,

So my case came with 4 3 pin fans but the side fan just died. I'm going to switch it out for a 4 pin fan so I can control the speed but I don't have enough slots on my mobo so I'll be using a splitter. The splitter will go onto the 4 pin slot and fit both my new 4 pin fan and my old 3 pin case fan.

My question is will I be able to control my speed like this and are there any dangers with a 3 pin and 4 pin fan using the same splitter or am I good to go?

 

[hotaru.hino]

No. One or the other will be at 100% all the time.

EDIT: Actually, 4-pin fans may become voltage controlled if there's nothing on the PWM line, but I can't confirm this.

 

[Paperdoc]

The speed of fans CAN be controlled by the mobo headers no matter whether they are 3-pin or 4-pin. The secret is the METHOD of control is different, so each mobo fan header needs to be set to the correct MODE. You must use either PWM Mode for 4-pin fans, or Voltage Control Mode (aka DC Mode) for 3-pin fans. Because they are different, you generally can NOT mix the two fan types on the same mobo header.

When you do the wrong way, this is the result:
3-pin fan plugged into header set to PWM Mode = that fan always runs full speed - no control.
4-pin fan plugged into header using Voltage Control Mode = fan DOES work under speed control, but this is not the ideal way to use this fan.

You have a system with all 3-pin fans using Splitters. However, your post suggests that you do NOT have their speeds under automatic control and you want to get control, so you plan to buy a 4-pin fan. That will NOT do what you want. Your first step should be to go into BIOS Setup to the fan headers you are using now with your fans and ensure that each is configured to use Voltage Control Mode (aka DC Mode). THAT is how you can have speed control of those 3-pin fans.

Now, with that working, you need to replace ONE of these fans. IF you use a new 4-pin fan it will work, but not ideally. IF you buy a new 3-pin fan it WILL work perfectly just as the old ones do now with the altered header configuration. And it may be a bit less expensive.