how can i tell if the thermostat on my water heater is bad?

Answer 1

You can use a multimeter to check the water heater's thermostat, and heating elements.

Most electric water heaters have 2 heating elements, one about the mid-height of the tank, and the other is lower. Typically, one thermostat will control both.

The thermostat is easy to replace. Shut the power off to the water heater, disconnect the wires to the thermostat, and unscrew it. Take it to the hardware store, and buy the same kind. If you think you might not remember how the wires were hooked up originally, it's handy to take a pic (polaroid or digital camera)

Oh, typically, when a thermostat goes 'bad' - it just quits working altogether. So that's the first sign.. no hot water, hehehe. Use the multimeter, as I mentioned to check not only the thermostat, but also the heating elements.

Good Luck

Answer 2

turn it up, if it starts heating again its good,
turn it back to original setting it should shut off,