I am replacing the heater but I am trying to save on the thermostat; how should I test the thermostat?
Please help,
Safety thermostats can be tested for continuity with a multimeter. A good one will read closed or shorted. The operating thermostat can also be tested with a multimeter, but you would need to get it hot to verify it opens, and back closer to room temperature to verify it closes. If you are replacing the heater, I assume you found it to be bad, so the other components must be working if power is getting to the element.