Hot Water Heater Thermostat Testing

Hot Water Heater Thermostat

Below you will find step by step instruction for testing a  hot water heater thermostat.

This page is for duel element water heaters, however, single element heater thermostats are checked the same way.

How to test a thermostat

The test below will be performed with the power on. You will need a multimeter and know how to use it safely.

You can test water heater thermostats with the power off if you prefer. Go to test water heater thermostat.

Don't let anyone distract you while your testing. Be sure that no one gets near the water heater until you're finished.

Please read the entire guide before starting.

Duel element residential water heater

Both elements do not heat at the same time. Starting with a tank of cold water, the upper element will heat the water in the top half of the tank. When the upper thermostat is satisfied the upper element will shut down and the lower element will begain heating.

This following test will not work if the water temperature is extremely hot. If this is the case you may have a grounded element. Visit water heater element testing for more information on grounded elements.

Water heater elements are easy to check. I recommend that you check the elements before testing water heater thermostat.

Test hot water heater thermostat (upper)

Turn the water heater power off. Remove both access panels, insulation and plastic safety covers.

Check to ensure that the reset button has not tripped.

Use a small screwdriver to set the upper (top) thermostat temperature to the highest setting (see pic).

Set the lower thermostat temperature to the lowest setting.

Turn the water heater power on.

Check the two wires above the reset button to be sure their is voltage coming into the water heater (see pic).

This water heater is 240 volts. Voltage at the elements on this water heater should be 240 volts.

Place the multimeter probes on the upper element contact screws (see pic). If you do not have power at the element the thermostat needs replacing

If you do have power its time to check the lower thermostat.

Test water heater thermostat (lower)

Set the upper thermostat temperature to the lowest setting.

You should hear the thermostat click off as you turn the dial. If you don't hear it, give the water time to heat up and then continue.

Set the lower thermostat temperature to the highest setting

Check the lower element for voltage. If you have power at the element allow the water to warm a bit. Lower the temperature on the thermostat. You should hear it click off. The thermostat is good.

If you do not have power at the element go to the next step.

Test the lower thermostat for power. Place one multimeter probe on the top contact screw and the other probe on the water tank (see pic). It should read 120 volts. If you do not get a reading replace the upper thermostat. It is not sending power to the lower thermostat.

If you have power go to the next step.

Place one meter probe on the lower contact screw and one probe on the water tank.

You should have 120 volts, if not, replace the lower thermostat

Other pages you might be interested in.

Replacing a hot water heater thermostat - Step be step guide for replacing an electric water heater thermostat.

Water heater gas thermostat - How to check or replace a water heater gas valve/thermostat.

Water heater temperature -How to check or adjust water heater thermostat temperatures.

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