Question 6 Case Fans and Only 3 SYS_FAN headers.

Jan 16, 2021
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Hello Everyone,

I have just built a new PC for myself... but the only thing that always bothers me is the FANS.

I want to have 6 case fans in total but only have 3 SYS_FAN connectors on the Motherboard (B550 AORUS ELITE AX V2).

Can someone advise what's the best option for myself in this case? I would like to have "some" kind of control over fans, so they don't run at the full speed.

Currently I have three fans on the front (Corsair RGB iCUE) and I bought an additional BeQuiet Shadow Wings 2 for the back ( I will be buying 2 more fans after I decide how to plug them in...). So 2 of the front Corsair fans are plugged directly onto the motherboard and 1 front Corsair fan + BeQuiet Shadow Wings 2 are connected to Y splitter which I bought on Amazon (yeah I know you can overload them etc. just bought it to see if it works at all). I have noticed that the fans connected to the splitter have a bit lower RPM (700 RPM) and the other two connected to the motherboard directly have (760 RPM) even after having the same settings in BIOS - so this is not a best solution straight of the box and I'm actually worried that I have broke the motherboard already - hopefully once splitter removed and fan plugged straight into the motherboard will have the same RPM as the other two on the front.

I'm now stupid - Molex will run fans on the full speed (and I would need to but it separately) - so this is stupid solution.. Corsair Commander Pro costs 60 pounds - a bit too much.

Is there actually any sensible solution to this problem rather than looking for the motherboards with 6 SYS_FAN headers next time?

Thanks in advance.
 

Viorala

Prominent
May 20, 2019
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There are hubs for regular fans (non-rbg and non-arbg) but they're around $40 usd which is a bit extreme imo. I was looking at DC fan hubs though, you might want to look for PWM fan hubs.
 

Paperdoc

Glorious
Ambassador
You can do this with simple Splitters. The worry you express is not an issue. Any mobo header can accept coming back to it the speed of only ONE fan. So any Splitter (as you have) will only send back one speed. Look very closely at the two output connectors for the Splitter that is feeding the two different fans. ONE output only will have all four pins. I'm betting you have the beQuiet fan plugged into that one. Since it is different from the Corsair units it will run at a slightly different speed from them even for the same input signals. I bet if you plug the Corsair fan into the output with 4 pins, it will show you the same speeds in both headers.

There ARE two issues you need to give attention. One is that 3-pin fans and 4-pin fans (the MOTORS,not the lighting cables) require different methods of speed control by the mobo header. So ideally you should have only one of those types. So, are ALL of your 4 fans of the 3-pin or 4-pin motor type? Look at the connector on the end of each motor cable - do they have 3 holes or 4? As long as they are the same, you can do the rest easily. Just make sure any added fans are also the same.

A mobo header normally can supply power up to a max load of 1.0 A for all fans connected to a single header. (Separate 1.0 A limit for each header.) For the motors only (not including lighting power which is supplied on a different cable from a different header), the max current on today's fans is usually 0.10 to 0.25 A per fan, so two of those on a single header is surely OK. Thus, if you buy one more Splitter and connect two fans each to your three mobo SYS_FAN headers and configure them all the same, you have no problems. See your manual, p. 31 regarding the item Fan Control Mode. If your fans are all 3-pin, set that to Voltage; for 4-pin fans, set it to PWM.
 

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