Fan splitter cables

Big Frank · 20 Dec 2018 at 11:13

This should be a quick one.

Just ordered 2 new corsair blue LED fans and a 2 way splitter cable. These are 3 pin fans.

My question is will the bios still control both fans that are plugged into the single header?

Matthew Quinn · 20 Dec 2018 at 11:17

I believe the power would be less, so you're best buying an adaptor for the second fan

Big Frank · 20 Dec 2018 at 11:37

Matthew Quinn said:
I believe the power would be less, so you're best buying an adaptor for the second fan

The fans only draw 0.23A each. What adapter?

bremen1874 · 20 Dec 2018 at 11:37

Assuming there's nothing unusual going on both fans will be controlled. Only one of them will return a tacho signal.

LuckyBenski · 21 Dec 2018 at 08:04

This is making the assumption your motherboard has DC voltage control on those particular fan headers. If you have that and it's enabled, everything else should be sweet. The motherboard will take a speed reading from one of the fans - you can tell which one by finding which of the extended plugs has the 3rd wire left in. One probably won't.

Big Frank · 22 Dec 2018 at 00:34

Cheers for the replies. My mobo is a Asus z370-p I can't find any documentation that says if it has DC voltage control. I think it does though.

lee32uk · 22 Dec 2018 at 01:04

Big Frank said:
Cheers for the replies. My mobo is a Asus z370-p I can't find any documentation that says if it has DC voltage control. I think it does though.

Yeah that board has PWM/DC options in the bios. Just had a look at the manual on Asus website.

maklabouhlel · 23 Dec 2018 at 01:36

If voltage is set too low then fans may not run because the current is shared so you may have to increase voltage to run both fans.

LuckyBenski · 23 Dec 2018 at 01:40

maklabouhlel said:
If voltage is set too low then fans may not run because the current is shared so you may have to increase voltage to run both fans.

So long as the current doesn't exceed the rated limit of the fan header, it will behave exactly the same as for one fan. Current is shared but unless the header is overloaded, it will happily supply 2,3 or 15 fans at the same voltage as for one.

maklabouhlel · 23 Dec 2018 at 01:43

Say fan control is enabled and the header is providing 5 amps then it's 2.5 each which may not be enough. It's something I've personally experienced. The other way is to run at full speed without fan control then both fans will run. It may work with fan control enabled but sometimes after a cold boot it may not until the system warms up and current is increased.

LuckyBenski · 23 Dec 2018 at 03:41

maklabouhlel said:
Say fan control is enabled and the header is providing 5 amps then it's 2.5 each which may not be enough. It's something I've personally experienced. The other way is to run at full speed without fan control then both fans will run. It may work with fan control enabled but sometimes after a cold boot it may not until the system warms up and current is increased.

I disagree with almost all of this, sorry. Fan headers aren't current-controlled, they're either voltage-controlled or a PWM signal is varied. Current is drawn not pushed. Current is shared, but two fans will present half the resistance and so draw double the current from a given voltage. Half of double the current is, yes, the same current per fan as a single fan on its own.

You're overthinking this. Maybe you've had fans which have a high starting voltage.

maklabouhlel · 23 Dec 2018 at 11:09

LuckyBenski said:
I disagree with almost all of this, sorry. Fan headers aren't current-controlled, they're either voltage-controlled or a PWM signal is varied. Current is drawn not pushed. Current is shared, but two fans will present half the resistance and so draw double the current from a given voltage. Half of double the current is, yes, the same current per fan as a single fan on its own.

You're overthinking this. Maybe you've had fans which have a high starting voltage.

You're right that's why I said I had issues after a cold start because the low temps meant low voltage so only one fan would run. As the system warmed up, both fans would start running.