Question Define 7 + Aorus Elite case fan problem

[quiciuq]

Hi.
I have set up my rig with X670 Aorus Elite AX in Define 7 case. Apart from AIO CPU cooling and GPU's own fans, I use stock fans shipped with the case (three Dynamic X2-GP14, 120 mm). They are 3-pin fans, meant to be connected to the in-case fan hub. The hub has its own power supply (SATA) and uses 4-pin connector to communicate with motherboard (only two pins are actually used). MB has 3 sys fan connectors and I used SYS_FAN 3 (because cable length).
Now, their behaviour is weird: when I enter BIOS and set the System 3 (SYS_FAN 3 connector) input to PWM, everything runs quietly, I can control fans' speed, no problem (they run in sync, being seen as a single fan, which is to be expected). But the moment I leave BIOS, they just go to 100% and stay there, no matter what. CPU and GPU fans behave normally.
What's more, Gigabyte Control Center (and any other fan software I tested) see the System 3 as idle at 0 RPM and no matter what I do, they still go brrr.

My theory is that they stop being seen as PWR and simply use voltage, but I have no idea why. What I am doing wrong?
I appreciate any help.

 

[Paperdoc]

Normally you cannot control the speed of 3-pin fans from a common 4-pin fan HUB because such a device works only with 4-pin fans. HOWEVER the manual for the Define 7 case indicates that the Hub provided does a special thing. It CONVERTS an input PWM speed control signal to a Voltage Control Mode signal for all its fans, and thus CAN control the speed of those fans. You have verified this in BIOS Setup - there you can control their speeds. So the puzzle is: why is speed control lost when you exit BIOS Setup?

The Hub is plugged into the mobo SYS_FAN3 header. The three fans in question are plugged into the three 3-pin ports on that Hub, and there are NO other fans plugged into that hub, right? Now, that Hub also has 4-pin fan output ports, and ONE of those is designated for use with the CPU cooler but you are NOT using that port. This means the Hub does NOT send back to its host header any speed reading from any fan because only that one port will send its speed signal back to the host header. There is nothing wrong with that, except for a couple small notes (below). BUT it is causing an effect on fan speed control that I believe you can fix.

In the configuration options for SYS_FAN3 there are three choices under FAN/PUMP Control Mode: Auto, Voltage, and PWM. Default setting is Auto. In that Mode at every start-up the header starts the fan at full speed, then sends out a PWM-style signal to tell it so slow down and watches the result on the fan speed reading. If the fan does slow down it must be PWM type and that's the end of that. BUT if the fan does NOT slow down it must be an older 3-pin fan that requires Voltage Control Mode signals, so it switches to that Mode. That means that it will NOT send out any PWM signal. HOWEVER, that Hub NEEDS a PWM signal to do its own speed control work; without that signal it will only send out full speed signals to all its fans. I think that is what is happening to you.

So, change a couple details of configuration on the SYS_FAN3 header. Set Fan Speed Control to Normal so it will use the pre-programmed set of automatic controls. Set Fan Control Use Temperature Input to the Motherboard sensor, and not the one inside the CPU chip. Set FAN/PUMP Control Mode to PWM. Set FAN/PUMP Stop to DISabled so the fans never stop. Set FAN/PUMP Fail Warning to DISabled so it will not send you an alarm when there is NO speed signal sent back to it. Once you have all these set, use Esc back to Main Menu, then the F10 key to reach the Exit Menu. There choose Save & Exit Setup to save these settings and reboot. This should set the header to always send out PWM-type signals to the Hub so it can control automatically the speed of its fans, and ensure that those speeds are based on the cooling needs of the motherboard (and all its components), rather than on the CPU chip alone.

 

[quiciuq]

Thanks for the in-depth explanation, you rock.

Your solution though did not work - this was the way I set it up in the first place (I mean BIOS config). But as you pointed out, the mobo do not get proper response from the hub as it does not have PWM fan connected and can't provide the proper data, I don't have 4-pin fan available to test it out, but in the future I will try to connect one to the hub and try again.

For now, the soultion was to connect fans directly to the mobo, bypassing the hub entirely. The connections fit, the PWM pin just stands out unused and the BIOS allows to switch between voltage and PWM control, so it works just fine. I intend to fit in two more fans in near future and I don't have enough headers, so I guess I will have to solve it in the future, but this time with proper PWM fans and see how it works.

For this reason I consider it to be a temporary workaround. I'm not sure how to mark it in the post, so I'll leave it as is for now and update it after the upgrade.

 

[Paperdoc]

Because 3-pin and 4-pin fans require different types of signals (MODE setting of a header) you cannot mix both types on one header. So IF you get tw2o new FOUR-pin (PWM type) fans, you will need to arrange those two on one header set to PWM Mode, and the 3-pin fans on other headers.

To do this you will need a different type of device to connect more than one fan per header. It is a SPLITTER, not a HUB. A Splitter is a simpler device, but WATCH OUT - sellers use those two labels interchangeably and they are wrong to do that! A Splitter has one input to plug into a mobo header, and two or more outputs for plugging in your fans. It has NO other connections. A HUB has that third connection to a SATA power output from the PSU. Splitter example

https://www.amazon.com/Splitter-Extension-Converter-Sleeved-Computer/dp/B0B398L8V5/ref=sr_1_33?crid=KNZMSDZ5RXV4&keywords=pc+fan+splitter+4+pin&qid=1680275317&sprefix=4-pin+fan+splitter,aps,106&sr=8-33

That's a 2-pack of 3-output Splitters of the 4-pin type. You CAN use those for 3-pin fans.

The key difference with a Splitter is that all the power for the fans comes from the host header, none from the PSU. So you are limited to a max load of 1.0 A current for all fans to ONE header. Almost all fans now pull a max of 0.10 to 0.25 A per fan, so two or three of these is easily OK on one header using a Splitter. For your case, the reason a Splitter is the right tool is that it passes to all its fans the VOLTAGE from the mobo header's Pin #2, and that VARYING Voltage (using the Voltage Control Mode or DC Mode of the header) is how the speed of 3-pin fans is controlled.

Your simplest plan would be to get two Splitters like that, and two more THREE-pin fans. Use the Splitters to connect a couple pairs of fans to two of your headers and a fifth to one other header. Or, three each to two headers, etc.