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Stop fans on PWM headers

MeanMachine2k18
Level 7
To reduce noise under light loads I wanted to stop the case fans with QFAN in the Bios of my ROG STRIX Z390-I GAMING (MINI ITX) motherboard. However it doesn't seem to be possible to stop the fans using the fan header in PWM-mode. Using DC-mode I can check a box with auto fan-stop.
-> Why isn't it possible to stop a fan in PWM-mode using QFAN?

Because the Z390-I board only has three PWM headers (CHA_FAN, CPU_FAN and AIO_PUMP) I connected a case fan to the AIO_PUMP header. When selecting for example 20% fan speed, the fan connected to the AIO_PUMp header continuously spins at +1400 RPM. The auto fan-stop feature is not available for this header, even under DC-mode.

Seems that I need to use a third party app like Speedfan or connect both casefans to the CHA_FAN header in DC-mode to turn them off... .
Any ideas?

I use the fans that came standard with my NZXT H200 case, 4-pin NZXT Aer P I think.

Thanks,
MeanMachine
13,072 Views
5 REPLIES 5

Ch3vr0n
Level 10
You shouldn't attach a fan to the AIO_Pump header, that's not what it's for. That header is specially designed to attach SOLELY a liquid pump motor to, because that header ALWAYS needs/gets 100% power, regardless of setting. You need to connect the case fan to CHA_FAN that's what its (designed) for. A chassis (case) fan. CPU_FAN is as the name sais for the fan controlling the CPU, and AIO_PUMP exclusively for the motor of a liquid cooling system. It'll be in the manual too.

Page 1-13 of your manual:

Connect the pump cable from the all-in-one cooler (AIO cooler) to the AIO_PUMP header, and connect the fan cable to the CPU_FAN header. If your AIO cooler has more than one fan, you may need to use a pigtail cable to connect the cooler to the motherboard.

If you want to control more than 1 fan on CHA_FAN you'll need to use a fan cable splitter. You're using the header wrong, and asking something of it which it's incapable of doing.

I was fully aware what the manual said but tought I could address it as a normal fan header. Too bad the small form factor means taking the motherboard out to swap headers :p.

This doesn't resolve the fact that I need to switch the header from PWM to DC mode in order to get the fans to stop. Any ideas on that? I've read that some fans (e.g. Corsair ML 120) make more noise when operating under DC-mode.

Thanks for the feedback

Ch3vr0n
Level 10
when you swap header, pwm mode should work just fine, as intended. I've no clue about ML's or the old school DC current method. i use my LL120's & 140 in PWM mode on a corsair commander pro. Maybe you should go that route. That way you can fine-tune them and set them to 0 under certain conditions yes.

JustinThyme
Level 13
I’ve not heard of or seen a PWM fan go to zero. Depending on the fans if you take away to PWM signal you get either full bore or roughly 30%. PWM allows for much lower speeds than *voltage control as they have 12V all the time and you are simply controlling the duty cycle. DC fans hit a stall point eventually and running them too low will result in the motors overheating. Choosing the right PWM fans is the challenge. I’m running 20 PWM fans controlled with an aquaero using liquid temp for a reference for all but one that pulls in air from the rear, it’s controlled by the MOBO temp. Either I’m deaf of this set up works very well because for all but very *high load situations the liquid temp doesn’t go up with the fans at 30% which isn’t completely silent but not far from it. My twin D5 pumps that I have tweaked to offset harmonics and cancel out as much as possible are the only things I can hear until the liquid temp increases and the rad fans ramp up.*

@Ch3vr0n......how did you get a commander pro to work? I tried one but no matter what use for a source the fans ramp up and down. Not like min to max but enough that it’s annoying as h3ll. **The aquaero I’ve had for some time works flawlessly



“Two things are infinite: the universe and human stupidity, I'm not sure about the former” ~ Albert Einstein

Ch3vr0n
Level 10
@justinthyme according to corsair forums the automatic preset profiles are known to be buggy. It's something in the firmware they think. I just made my own. Set all fans at 25% and it's dead quiet. While still cooling just as good.