Question CPU fan header is not working on my AB350 Gaming K4 ?

Jul 20, 2022
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after some PC (physical) cleaning, I noticed, that two fans from my AIO liquid cooling are not spinning (I don't know for how long, most probably after cleaning). I swapped the AIO cable from CPU_FAN1 to CHA_FAN3 and it works, so probably the header is not working correctly. I noticed, that a smaller (120 instead of 140) fan works on this header, but very slowly. I also noticed, that if I plug it on an angle (probably the 4th pin doesn't connect) both fans will spin at full speed. I also noticed that temperatures displayed in UEFI are strange (65535, so maximal value for integer 16 bit), but temperatures displayed in OS or memtest are realistic.

Update: other fan controllers are probably also faulty, fans are just spinning at high speed. The only way I can control them is to use a fan controller from my case (Lian Li LanCool II Mesh).

I tried:

- resetting UEFI (shorting pins, no battery, no PSU cable)

- searching for a header mode setting, but there is no such thing in my UEFI. According to some info found on the Internet, it is only PWM mode

- memory test went ok

- setting fan speed to full speed or to profile with speed based on MB temperature.

Systems (Windows 10, Linux) are stable on this machine

Can I do or check something more? Or it's probably a broken header and I should just use another fan header.

my machine:

- Motherboard ASRock AB350 k4 gaming

- Fans from Arctic (PWM 140 and 120)

- AIO Arctic Liquid Freezer II

- CPU Ryzen 1700X

- BIOS 5.80, cannot update because of the CPU

The screenshot from ASRock F-Stream doesn't look right
 

Cyberat_88

Distinguished
Apr 9, 2011
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It's a bent pin or bad soldering on MB if you can get it to run right at a certain angle. You can take the MB to a shop to fix it or RMA if in warranty.
CPU fans are something you want the MB in charge of not some external utility. Only as last resort, if you set them to 100% at all times.
 
Jul 20, 2022
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I don't think it runs right when I plug it at an angle- it runs full speed, so It's like it's running on 3 pins at full speed.
I plan to go to a shop, but I need the PC for work. It's 1st ryzen MB so it's a long time after the warranty expired.
I think temperature sensors in the MB may be broken too- maybe they are affecting fan control (but I tried setting full speed and it did not work).
I'll check how the fan will behave if I'll set low speed and bend the plug. Maybe It's time for a new MB
 
Jul 20, 2022
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I think CHA_FAN1 works exactly like CPU_FAN1 (can't even drive a 140 fan) and CHA_FAN3 drives at full speed always. Looks like every fan header is broken somehow. Tried to get the approximate cost of repair but got no reply for now. Maybe it'll be easier to just buy used MB.
 
Jul 20, 2022
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I bought a used one (ASUS this time) to have a working one and I'll try to check/replace mosfets if they are fried but I think it could be a broken PWM controller.
 

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