Quick question for my own knowledge.

[Aire]

Hi guys, as some of you know my fault finding is pants so just want to clarify something.
Called to another vokera unica today. Fault code 73 relating to return pipe thermistor.
Removing combustion chamber cover and there was a little weep coming from the return pipe connection into the heat ex.
This had dripped onto the thermistor and corroded one of the connections and had broke off.
Not a problem I'll pick another one up tomorrow to get boiler working while customer decides what to do with boiler.
To try and get them heat for tonight I tried linking the thermistor out, which didn't work and got me thinking as to why.
Am I right in thinking the pcb needs to know what temperature the the return water is so it can modulate the burner to suit, so linking the wires is pointless as no temp reading can be picked up?

Thanks.

 

[ShaunCorbs]

Works on resistance so linking wouldn’t work but linking with a resistor would depending on the k valve

 

[Deleted member 32524]

Correct. Thermistor uses resistance readings in KOhms that change with temperature and the pcb reads the resistance and adjusts the burner accordingly.

 

[Aire]

Great, thanks guys.