Victron Virtual Switch (Number Input) write not working

Node-RED
1

I’m trying out the new Virtual Switch node set up as a Number Input. It works fine the other way around: if I change the value in the Victron GUI, it immediately spits the new value out on output 3 like it should.

Where I’m stuck is setting a value from Node-RED. My test input function for the node looks like this:

msg.payload = {
“/SwitchableOutput/output_1/Value”: 4
};
return msg;

When I trigger it the node status says “Updated 1 path (101)” , the payload passes straight through to output 1, and the debug window throws:

Failed to apply debounced value for /SwitchableOutput/output_1/Value: Property SwitchableOutput/output_1/Value not found in properties.

Nothing changes in the GUI the value remains unchanged.

Reading the value from the GUI works perfectly, it updates Node-RED straight away. But writing back just doesn’t seem to do anything.

Am I doing something wrong here, or is writing to Number Input virtual switches from Node-RED not actually supported yet?

Any pointers would be much appreciated.

Meini

2

I think the path for the numeric input is “/SwitchableOutput/output_1/Dimming”, not Value.

3

Thank you Nicolas! I really appreciate your fast response.

I would have never guessed. How do you know this? Trial and error? I can’t find any documentation going into those things other than the ones inside Node-RED and that’s not explaining much about the input values.

4

I had the same problem with the slider, where the path in the Node-RED documentation is wrong.
I find the easiest way to check is to connect via ssh on the VenusOs device and use dbus-spy to look what path are available on dbus for the node I’m trying to use.

5

Did you try the help tab in nodered? Seems pretty self-explanatory:

Screenshot 2026-03-22 at 09.02.53
Screenshot 2026-03-22 at 09.02.53616×714 24.8 KB

6

Yes, the thing is the inline documentation of the “Basic slider” is wrong (still is in 3.80~7) : Value instead of Dimming

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image690×410 42.4 KB

In 3.72~1 the “Numeric input” documentation still talk about Value, but it’s corrected in 3.80~7.

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image1390×1080 115 KB

This can be confusing and maybe others are wrong too, so I check before creating my flux.

7

There have been a few fixes in 3.80 which don’t appear to be backported to 3.7x.