Sharing a PC motherboard PWM signal

[ttl]

Hello,

I'm trying to control the speed of 5 PC fans via PWM (all at the same speed). My motherboard only supports PWM signals on the CPU FAN header, but it has 4 other 4-pin headers which don't actually work as intended (they have voltage control).

So what I'm thinking is that I can connect the PWM signal to all 5 fans, and connect each fan's tachometer to a motherboard header, and a separate 12V/GND from the power supply. I have attached a rude schematic of what I'm trying to do.

Can you tell me if this will work properly, before I start crimping this mess?

Thanks.

[Psi]

I cant see any problem doing that.

[Mr.B]

Yes, that will work.
I have done it before.
However, be aware that all the fans speeds are dependant upon what the motherboard thinks the CPU temperature is.
This may be quite fine for your requirements...

[ttl]

However, be aware that all the fans speeds are dependant upon what the motherboard thinks the CPU temperature is.
This may be quite fine for your requirements...

That's exactly what I want.

Thanks!

[Kevman]

Did you check the BIOS settings page? Many motherboards have an option in the BIOS to switch fans between 3-pin (voltage) and 4-pin (PWM) mode.

[Mr.B]

Did you check the BIOS settings page? Many motherboards have an option in the BIOS to switch fans between 3-pin (voltage) and 4-pin (PWM) mode.

Good point, however the OPs drawing would indicate that the 4 headers concerned are only 3 pin.