How do you troubleshoot a thermostat on an electric water heater to verify if its working or not? Bench testing and testing on unit?

This can be done two ways, either with an ohm/continuity meter or with a voltage tester.

Using an ohm/continuity meter, power must be off, and best to disconnect the wiring to the stat. Connect the leads to the output terminals of the stat, and raise and lower the stat adjustment dial to see if the stat is opening and closing.

The downside to this is the stat is looking for higher than normal ambient temperature, and difficult to be sure the stat is sensing the hot water.

If the water heater is in operation, I leave the power on, and use a voltage meter to test the voltage output of the stat, checking to see if the stat is opening/closing at the temperatures it is sensing from the tank as I am turning the temp adjustment dial.

Many stats are only lableled Low-Medium-High. Never really knew what his means. Not very scientific. I like the ones that have the actual temperatures stated on the dial incrementally 90 Deg,120 Deg, etc.

Does this make any sense?