CPU_FAN and AIO - fans spin on boot then stop

[Kenai]

Hi, bit of a problem that my Google skills are failing me for...

I have a Gigabyte B550 AORUS Elite AX V2, Ryzen 5600X with an EK 360 All In One DRGB Cooler.

AIO pump on CPU_OPT, 3 fans on CPU_FAN via supplied 3 way splitter cable.

The trouble I'm getting is that the 3 fans spin up to full speed on boot and then stop. Beyond boot, I can't get them to spin up via SmartFan in Gigabyte SIV or SmartFan in the BIOS.

The PC seems to recognise that there is a fan of some description as it shows a fan symbol in the SIV SmartFan page, rather than a '?' as it does for the SYS_FAN headers that have nothing connected.

I've tried removing the splitter in case that's preventing some sort of speed feedback signal that would cause issues but the symptoms are identical whether 1 fan direct or 3 via splitter.

AIO pump via CPU_OPT behaves as I would expect, controls adjustable in software and BIOS and it responds when adjusted (though I'm leaving it as full speed fixed, read the pump isn't really meant to be speed controlled).

I've tried turning off AMD Cool and Quiet as per one suggestion I found in the BIOS but no difference.

When using 'Calibrate' in SmartFan, the SYS_FAN3 connected case fans ramp up and down but zero reaction from CPU_FAN.

I'm hoping I've missed something daft here, as it's been a good few years since my last build but this is quite frustrating.

 

[Kenai]

They're the 120mm EK Vardar DRGB PWM that come with the AIO Cooler.

EK Water Blocks EK-AIO 360 D-RGB All In One CPU Water Cooler - 360mm

Order EK Water Blocks EK-AIO 360 D-RGB All In One CPU Water Cooler - 360mm now online and benefit from fast delivery.

www.overclockers.co.uk

Header is in 'Auto' in BIOS. I will try setting to PWM directly.

I'll try and hook one up to a SYS_FAN header, though the fact they all spin up for a few seconds on boot would suggest the fans themselves are functional.

 

[Kenai]

So, changing to PWM rather than Auto hasn't changed the behaviour.

Plugged one into SYS_FAN, behaves as expected, adjustable via software etc.

I suppose the lazy option is just run all the fans off a SYS_FAN header instead but still... It should work on CPU_FAN and I want to know why it doesn't

 

[Kenai]

My question is why do you want to run them all off the cpu fan header and not on their own sys headers?

If you just want more fans as you have no sys headers left then get a fan hub?

Because I had made the assumption that the fans dedicated to the CPU cooler would be better to run from the CPU_FAN header, with the SYS_FAN headers used for general case ventilation fans. They would then (if it worked) run on a profile based on the CPU temp, whilst the SYS_FAN headers can be profiled against general case temps.

Regardless, whether one fan or three are connected to the CPU_FAN header, the behaviour is identical.

Connecting to SYS_FAN and throwing in hubs feels like a bodge that's avoiding figuring out why the CPU_FAN header isn't working correctly in the first place.

 

[Kenai]

Yes, I could do that.

But that doesn't resolve why the CPU_FAN header isn't working correctly with any fans, which is the problem I'd like to understand and hopefully solve, rather than just bypass.

 

[Kenai]

I'll try that software if/when I get chance during the weekend (weather being nice, I might not get away with hiding away fixing the PC!), though I'm not holding out too much hope that it's likely to do anything Gigabytes own fan control software isn't or can't do. As I've tried to adjust and control within the BIOS and the software based fan control already. I'll try it nonetheless, as it could shed light on things.

I'll double check all the curves etc. but 99% sure I'd disabled any zero speed modes.