Description

The Swimables SW-41-053 is a generic thermistor for MasterTemp and Max-E-Therm pool heaters. It is an aftermarket replacement, not the original manufacturer sensor.

What a thermistor does

A thermistor is a resistor whose resistance changes predictably with temperature. The heater control board reads that resistance and turns it into a water temperature. Every decision the heater makes about firing, holding and shutting down comes back to that one reading.

Why they get replaced

Sensors sitting in pool water drift and eventually fail. When they do, the heater is working from bad information: the panel shows a temperature the water is not at, the heater short cycles, will not reach setpoint, or throws a sensor fault. Replacing the thermistor is the usual first move once the wiring has been checked.

Generic or original

This is the generic version. The original manufacturer thermistor for the same heater electrical system is stocked separately if you would rather fit the factory part.