Not sure what I've broken - NF-A4x20 5V PWM on FAN0



  • OK, I've had this working fine previously with not problems, but after moving the duet wifi board into an new enclosure I cannot get the cooling fan to work.

    The fan itself is a NF-A4x20 5V PWM.

    I've connected the 5V to expansion pin 1.
    GND to expansion pin 2.
    PWM control to FAN0-.
    I have not connected the speed sensor.

    i've set up the fan on config.g with:
    M106 P0 S0 I1 F25000 H-1

    The fan will not spin at all, no matter what % speed I set it to.

    I've checked continuity of all cables and they are all fine.
    5V (ex P1) reads as 4.66V against GND (ex P2).

    If I connect a 12V blower style pwm fan (across VFAN0- and V_FAN (12V)) it runs as expected at M106 P0 S0 F500 I0 H-1

    The killer seems to be that if I just connect the Noctua fan to an Arduino and control it from there it seems to work fine.

    Any insight would be fantastic.


  • administrators

    Does the 5V fan run at full speed if you leave the PWM wire unconnected?



  • No. This is the same behavior on the arduino.


  • administrators

    PWM fans normally run at full speed with the PWM control wire not connected. Perhaps yours has developed a fault. Adding a pullup resistor (try 1K) between the PWM wire and +5V may get it working again.



  • This is working. Thank you. Only issue is that it will still run while the ATX power is off, but this will do until i have a replacement for it.


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