Question AMD CPU Fan flashing and not spinning fast

Mar 8, 2021
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Hello,

Today I bought a Ryzen 7 3700X Processor, and a ASUS - ROG STRIX B450-F GAMING AM4 Motherboard. The issue I'm experiencing is with the CPU fan. It flashes with the LEDs constantly, and it barely spins. I noticed this when I got the "High temperature" warning when booting it up.

I have tried plugging in an old fan, one with 3 pins, and it spun so fast it felt like it was going to take off from my hand. This leads me to believe the fan may be damaged? - But I bought it literally today.

I have tried playing with the Q-Fan Configuration settings - converting from DC to PWM modes and setting the fan profile to "Turbo", but without any result. I cannot use any third-party software to control the fans either, as I am about to install windows on the machine.

I get the following error when initially trying to get into bios:

CPU Fan speed error detected.
Ensure that the CPU fan is properly installed on the CPU_FAN header or adjust/disable the Fan Speed Low Limit option in the UEFI BIOS.
Press F1 to Run Setup.

I was really anticipating this build - and I would greatly appreciate any help anyone would be able to give.

Thanks,
Kacper
 

Lutfij

Titan
Moderator
Welcome to the forums, newcomer!

3pin DC fans on a PWM header will always make it run at full speeds since there's no signal wire to tell the motherboard and report back of any fan feedback.

Are you sure the fan is connected the right way on the header and that the LED header is plugged in the right orientation, meaning the arrow on the RGB header? What BIOS version are you currently on for your motherboard? You might want to also see if your cooler's mount is proper and use HWMonitor to look at your CPU temps when the "High Temperature" comes about.
 
Sorry but that's just not true. 3pin DC fans do have rpm sensor connection/wire, what's missing is PWM connector/wire to regulate frequency and length of signal to motor to add to voltage regulation and speed that way. They can still be used in 4 pin header and get speed regulated by voltage. Only thing that may have to be done is to set in BIOS that header to DC instead of PWM control if there's no auto setting.
 
Mar 8, 2021
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Hi.

My cpu fan is connected to the CPU_FAN header. The fan does not have the rgb power connection cable.

I am using version 2.17.1246 on the BIOS.
 

Krotow

Commendable
Oct 2, 2019
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Sorry but that's just not true. 3pin DC fans do have rpm sensor connection/wire, what's missing is PWM connector/wire to regulate frequency and length of signal to motor to add to voltage regulation and speed that way. They can still be used in 4 pin header and get speed regulated by voltage. Only thing that may have to be done is to set in BIOS that header to DC instead of PWM control if there's no auto setting.
Correct. OP must change CPU fan control mode from PWM to DC in BIOS settings Q-Fan Configuration screen.
 

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