How to use Duex5 PWM port as a fan?

  • I need some help to use a PWM channel on my Duex5 board to drive my E3D Waterpump.

    I have a brainfart, so it's hopefully ridiciously simple once someone tell how 🙂

    I have allready used the last heater on Duex5 for my BLTouch, so this time I've disabled the Heater H6 (second to last on Duex5) to free up PWM channel 4, like this:
    M307 H6 A-1 C-1 D-1

    But how to setup a "fan" to use that particular channel?

    The build in Fan outputs on the Duex5 goes from P3 to P7, so how to use the above PWM channel4?

    I’m not going to need to adjust the speed on it, but will need it to activate thermostatically.

    That said, can the PWM ports be adjusted now? Asking academically as it didn’t used to be able to, but it was a thing that might be changed.
    Also would be nice as I have no free fan slots.

  • administrators

    Does the water pump draw more current than the fan outputs can provide? It's the starting current that is most critical.

  • I've decoupled it using a PowerExpander from That said it's only 12v 1amp.
    I'm running 24v so it made sense to decouple it for both reasons.

    Is it possible to use the PWM headers as "fans" and how?

  • administrators

    It's not currently possible to use the PWM headers as fan outputs controlled by M106 unless you recompile the firmware.

    Are you already using all 8 or 9 fan outputs?

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