@Dradle
My system is also 24v
I have a separate 12v power supply which runs the pump and some other 12v gear.
The pump I use is similar to this
It has a PWM output on both the pump and cooling fan.
In my setup I am using a fan output to control a the pump (which to the duet is just a thermostatically controlled fan). The setup to do so using 12v on a 24v system is here
I have fitted an inline temperature sensor to the hoses and control the radiator fan the same way as a thermo fan because it's not needed all the time and adds noise.
And finally I am about to add flow switch on the return line near the radiator to ensure that if a hose comes off, I can shut off the pump.
Because I have set up both the water pump and radiator fan as fans, I can monitor them in DWC
pump.gif.gif
and using the object model
om.gif.gif
So to answer your question on the setup
In my M950 F1 C"!fan1+^exp.e4stop" Q25000 I am using fan1 to turn on/off the pump and exp.e4stop to monitor the RPM of the pump impeller
If you're not controlling the pump from the Duet, omit the fan1
So you were close, but the input doesn't create a signal from lack of input. It just reports RPM (signal frequency).
It's up to you to interpret and take action based on that.
If you want a simple yes/no is it working? then use a switch, not a a flow sensor.
You could then set up a trigger macro and not worry about daemon.g
In my daemon.g I monitor the pump RPM using the object model and shut down if
The pump RPM is low and the hotend > 45C The radiator fan RPM is < limit The pump is on, but the flow return switch isn't active