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.
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.
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
Water heater elements are easy to check. I recommend that you check
the elements before testing water heater thermostat.
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
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.
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
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
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
Replacing a hot water heater thermostat - Step be step guide for replacing
an electric water heater thermostat.
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