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Easy Steps for a Hot Water Heater Thermostat Replacement

By Author Kevin L. Sharp

Posted on Last updated:

When your home’s thermostat quits working the way it’s suppose to, you want to make sure that you test the device before you replace it. Why? A good portion of the water heaters sold on the market today use both an upper and lower element. It’s essential that you figure out which element is in fact not working. To test your thermostat, you will need a multimeter and screwdriver. Follow the steps below:

Testing your water heater’s upper thermostat:

  1. Shutdown the power on your water heater.
  2. Locate the access panels and carefully remove them. Remove the insulation underneath as well.
  3. The upper thermostat now needs to be set to the highest setting possible. You can do this with a standard screwdriver.
  4. The lower thermostat now needs to be set to the lowest setting possible.
  5. Turn your water heater’s power back on.
  6. Locate the two wires positioned above the reset button and test them using the multimeter. Your multimeter should read 240 volts.
  7. Locate the upper element terminal screws and test them with the multimeter as well. You will know that your water heater’s thermostat is bad, because you won’t get any power.

Testing your water heater’s lower thermostat:

  1. While the power is still turned off, turn the upper thermostat to the lowest possible setting and turn the lower thermostat to its highest possible setting.
  2. With the multimeter, you now want to see if you are getting voltage from the lower element, and if in fact there is voltage, wait for the water to become warm. This may take just a few minutes.
  3. Now, you want to decrease the temperature on the thermostat. If the thermostat is operating properly, you’ll hear an audible click.
  4. If the multimeter reads that there is no voltage coming from the element, then you’ll want to test the lower thermostat for power. To do this, take one of the probes from the multimeter and touch it to the top contact screw. Take the other probe and touch it to the metal casing of the water tank. Your multimeter should read no more than 120 volts if it’s working correctly.

Replacing your thermostat:

  1. Shut off the power.
  2. Remove the water heater’s remove the access panel and safety cover.
  3. Carefully pull the bracket out that are holding the thermostat into place.
  4. Take the old thermostat out and replace it with the new unit.
  5. Put the brackets back on and make sure the wiring is reconnected in the same way it was disconnected.
  6. Put the access panel and safety cover back on and restore power.

If you are replacing a gas hot water heater thermostat, it’s important to note that the gas control valve, the thermostat and the heat limited device are all located on the outside of the tank.

Kevin L. Sharp
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