ASUS ROG Maximus XII "High Amp" fan header characteristics

[Thinkerion]

Hey,

 

I just filled my chassis with fans hoping to get some high static pressure at low fan speeds.

However i have not bought a fan controller since i figured the MB had enough headers for my build.

 

Problem is: I connected 3x 120mm fans on the "High Amp" fan header but trying to adjust the speed is impossible, it just stays at max speed.

Anyone know the problem and how to fix it?

 

 

[Jurrunio]

Maybe the port is set to PWM mode or PWM only, while the fans are DC only (i.e. 3pin fans)?

[Thinkerion]

1 minute ago, Jurrunio said:

Maybe the port is set to PWM mode or PWM only, while the fans are DC only (i.e. 3pin fans)?

Fan type is CM MF120 Halo so 4pin PWM fans. I should have said initially

 

[Jurrunio]

2 minutes ago, Thinkerion said:

Fan type is CM MF120 Halo so 4pin PWM fans. I should have said initially

 

What did you use to adjust the fan speed? The BIOS?

[Thinkerion]

3 minutes ago, Jurrunio said:

What did you use to adjust the fan speed? The BIOS?

AI Suite 3 from ASUS

[Jurrunio]

Just now, Thinkerion said:

AI Suite 3 from ASUS

then try the BIOS. Software tends to be less reliable.

[Thinkerion]

26 minutes ago, Jurrunio said:

then try the BIOS. Software tends to be less reliable.

strange seems to be locked at top speed both from bios and SW, although i did get some results for a small amount of time it just goes straight to the top when entering windows.

[Thinkerion]

28 minutes ago, Jurrunio said:

then try the BIOS. Software tends to be less reliable.

It is supposed according to SW to stop at less than 50C but it just keeps running at max.

[Jurrunio]

3 minutes ago, Thinkerion said:

strange seems to be locked at top speed both from bios and SW, although i did get some results for a small amount of time it just goes straight to the top when entering windows.

sounds like a conflict issue, did you uninstall AI suite?

 

[Thinkerion]

22 minutes ago, Jurrunio said:

sounds like a conflict issue, did you uninstall AI suite?

 

disabled it but still no standstill. actually i have a problem getting any of the fans to stop atm.. all fans are running even at 0%

[Jurrunio]

1 minute ago, Thinkerion said:

disabled it but still no standstill. actually i have a problem getting any of the fans to stop atm.. all fans are running even at 0%

not all PWM fans stop at 0%, some still run slowly. This is a kind of behaviour the fan designers can alter because the fan gets full 12V power at all times.

[Thinkerion]

3 minutes ago, Jurrunio said:

not all PWM fans stop at 0%, some still run slowly. This is a kind of behaviour the fan designers can alter because the fan gets full 12V power at all times.

See min and max speed values.. is it because i am pulling less than 1amp on it?

[Thinkerion]

10 minutes ago, Jurrunio said:

not all PWM fans stop at 0%, some still run slowly. This is a kind of behaviour the fan designers can alter because the fan gets full 12V power at all times.

Hmm, could it be that the speed reporting from the fan is faulty? that changing which fan it calculates the speed from could help?

[Jurrunio]

1 hour ago, Thinkerion said:

See min and max speed values.. is it because i am pulling less than 1amp on it?

That's a naming issue, what you're controlling here is PWM cycle. 23% means the extra pin gets power 23% of the time for example. It is not a speed reading. Think of it as the throttle of a car, how far you depress it doesnt equal to any certain speed or acceleration.

 

56 minutes ago, Thinkerion said:

Hmm, could it be that the speed reporting from the fan is faulty? that changing which fan it calculates the speed from could help?

Speed reading doesnt have anything to do with controlling PWM cycles.

[Thinkerion]

9 hours ago, Jurrunio said:

That's a naming issue, what you're controlling here is PWM cycle. 23% means the extra pin gets power 23% of the time for example. It is not a speed reading. Think of it as the throttle of a car, how far you depress it doesnt equal to any certain speed or acceleration.

 

Speed reading doesnt have anything to do with controlling PWM cycles.

Am I reading this incorrectly? If the PWM cycle is 20% this should not translate into either Power or Voltage but just the timing for On/Off.

Meaning that if I attach a 0,1Amp fan or a 3Amp fan, controlling the speed should work regardless?

 

As you can see from the picture above I have it marked for stopping fully at its current temperature, but it just keeps going at almost full RPM.

 

 

[Jurrunio]

4 minutes ago, Thinkerion said:

but just the timing for On/Off.

for dumb PWM fans, yes. Some are programmed to say, run 30% speed at 0% PWM. They have a dedicated chip for that rather than just connecting it to a switch. I dont know how your fan works however, so this is just an assumption.

 

4 minutes ago, Thinkerion said:

at almost full RPM.

now that's a problem. Is the BIOS using that header in PWM mode (rather than DC mode)? Are you using a splitter that doesnt split the PWM pin?

[Thinkerion]

1 minute ago, Jurrunio said:

for dumb PWM fans, yes. Some are programmed to say, run 30% speed at 0% PWM. They have a dedicated chip for that rather than just connecting it to a switch.

 

now that's a problem. Is the BIOS using that header in PWM mode (rather than DC mode)? Are you using a splitter that doesnt split the PWM pin?

I am actually wondering if the reading from the current fan with the 4th pin on the 3way splitter is not reading correctly making it run at max at all time.

Found some random paper saying that fans should run max speed if the control signal is missing. Guess that would be my next try, just rotate the connections, to the fans to give another fan the controlling signal pin.

[Jurrunio]

4 minutes ago, Thinkerion said:

I am actually wondering if the reading from the current fan with the 4th pin on the 3way splitter is not reading correctly making it run at max at all time.

Found some random paper saying that fans should run max speed if the control signal is missing. Guess that would be my next try, just rotate the connections, to the fans to give another fan the controlling signal pin.

Or even take away the splitters and try each fan individually

 

btw fan speed difference should be audible, dont rely on the software reading too much

[Thinkerion]

5 hours ago, Jurrunio said:

Or even take away the splitters and try each fan individually

 

btw fan speed difference should be audible, dont rely on the software reading too much

Well that was almost too easy.... just changed which fan had the 4th pin and it worked straight away.  PC nearly silent now