Confused...Fan splitter. What am I missing.

[gigabyte06]

I have two 3 pin fans that I want to hook up to one chassis fan header.
The splitter I see has a 4 pin connector for the MB and then one 4 pin connector and one 3 pin connector.

My case fan lines up with the 4 pin connector (pin to pin),but the other connector is missing a pin where it would line up with the other 3 pin connector. So basically that connector has a pin in one and two,then the third is empty and the fourth has a pin. Hope that makes sense.

 

[rgd1101]

http://www.tomshardware.com/answers/id-2319601/pin-fan-splitters.html

 

[boosted1g]

Its because of the way it is wired.

The missing wire is for tach signal FROM the fan. Having both of them send data (so voltage) back to the motherboard would cause false readings and probably even damage the fans since there is no diode prevent backflow of power.

 

[Paperdoc]

boosted1g is right. A splitter MUST be made so it cannot send to the mobo header more than one fan signal on Pin #3. when you use such a splitter, the system can show you the speed fo the fan that is plugged into the connector with all 4 pins. But the speed signal from the other fan is simply ignored and never measured or displayed. This has NO impact on fan speed control at all.

There is another matter, though, that you have not asked about. A 3-pin fan can have its speed controlled only by a mobo header that uses Voltage Control Mode (aka DC Mode). A 4-pin mobo header MAY do this, or it may be using PWM Mode. IF it uses only PWM Mode, that header cannot control the speed of a 3-pin fan, and it will always run full speed.Post back here the exact maker and model number of your mobo, and we can look up its manual and advise how to control your 3-pin fans.

 

[gigabyte06]

Asrock AB350 Pro4

 

[gigabyte06]

Found this in the manual....

3 x Chassis Fan Connectors (4-pin) (Smart Fan Speed
Control)
* CHA_FAN2 and CHA_FAN3 can auto detect if 3-pin or 4-pin
fan is in use.

 

[Paperdoc]

Good, you found the answer for yourself. The mobo headers will figure out that it is dealing with 3-pin fans and set themselves accordingly. So you're good to go using a 4-pin splitter to connect two 3-pin fans to either of the CHA_FANn headers. I suggest you go into BIOS Setup and ensure that the Temperature Source selected for those CHA_FAN headers is the motherboard, and not the CPU chip.

 

[Paperdoc]

Thanks for Best Solution.