RPM of DC fans alternate between a number value to NA in the bios

[Franzyngwie]

I'm using 3 lian li DC fans that came with the lian lancool 2 mesh rgb case. They are connected to the same CHA_FAN3 header in the asus tuf gaming b550-pro motherboard. When I enter the bios, the RPM of CHA_FAN3 keeps alternating from a number value (example 1000rpm) to the value "NA". The CHA_FAN3 fans are correctly functioning when I visually inspect them. The other fans (1 DC And 2 PWM) that are directly connected to separate mobo fan headers do not have this issue. Is this normal? Any clue on how to solve this?

[leclod]

Did you set CHA_FAN3 to DC mode and the PWM fans to PWM mode ?

I've had speeds not reporting correctly when being too low but 1000rpm is enough.

I guess you daisy chain your 3 DC fans. Only one of those reports its speed to the mobo, maybe switch those fans so another one reports its speed.

You probably have a utility that shows those speeds in Windows, what does it show ?

 

[Franzyngwie]

2 hours ago, leclod said:

Did you set CHA_FAN3 to DC mode and the PWM fans to PWM mode ?

I've had speeds not reporting correctly when being too low but 1000rpm is enough.

I guess you daisy chain your 3 DC fans. Only one of those reports its speed to the mobo, maybe switch those fans so another one reports its speed.

You probably have a utility that shows those speeds in Windows, what does it show ?

 

Yes, CHA_FAN3 is set to DC and PWM fans to PWM mode.

 

The windows software utility I'm using is called "Armoury crate". On this software, when I look at the fan speeds, The RPM on CHA_FAN3 are very disparate. Their values are around 1000, 900, 200 and even 0 RPM. On the other hand, the RPM on CHA_FAN1, CHA_FAN2 are almost constant (they hover around 450 RPM)

 

I've attached a x8 gif showing what i've explained above.

 

 

[leclod]

13 hours ago, Franzyngwie said:

Yes, CHA_FAN3 is set to DC and PWM fans to PWM mode.

 

The windows software utility I'm using is called "Armoury crate". On this software, when I look at the fan speeds, The RPM on CHA_FAN3 are very disparate. Their values are around 1000, 900, 200 and even 0 RPM. On the other hand, the RPM on CHA_FAN1, CHA_FAN2 are almost constant (they hover around 450 RPM)

 

I've attached a x8 gif showing what i've explained above.

You didn't answer to "Only one of those reports its speed to the mobo, maybe switch those fans so another one reports its speed."

[Franzyngwie]

12 hours ago, leclod said:

You didn't answer to "Only one of those reports its speed to the mobo, maybe switch those fans so another one reports its speed."

I swapped the fans around and the same problem happened. Also, I've noticed that this problem happens only once I daisy chain more than 2 DC fans... I should note that, by now, I've switched to a much cleaner, less noisy-ish, compact fan setup that is working without problems. However, I'm still curious as to why this problem happened...

[leclod]

On 10/13/2021 at 9:50 PM, Franzyngwie said:

I swapped the fans around and the same problem happened. Also, I've noticed that this problem happens only once I daisy chain more than 2 DC fans... I should note that, by now, I've switched to a much cleaner, less noisy-ish, compact fan setup that is working without problems. However, I'm still curious as to why this problem happened...

I made a mistake, DC fan don't have an RPM signal cable (the fourth).

Maybe it doesn't work because the signal gets scrambled when you daisy chain DC fans, it would work with PWM fans.