All I can come up with is that it is a resistor, and part of an
electrical-bridge where the
difference in thermal conductivity of the heat radiating from the resistor
is different if there is, or is not, liquid on the other side.

could be a thermistor which is a resistor that changes resistance with
temperature, then it could woek just as you say, the liquid keeps it
cool, when it runs outm the thermistor heats up....so the thermistor
can be both the heater and sensor in one component.

Mark