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How to Test Water Heater Thermostat – Step-by-Step Instruction

by James Antony | Last Updated: 2nd March 2021

In this article, you will find reply to your question about how to test water heater thermostat. We have prepared for you step-by-step instruction to help you to repair electric water heaters with upper and lower heating elements.

How to Test Water Heater Thermostat – Intro

We’ll have two thermostats, one to control each element. The thermostats maintain the water temperature inside the tank by opening and closing contacts that allow voltage to flow to the heating elements. The elements are designed to cycle one at a time. And the frequency of these cycles depends on how much heat is needed to help determine if a thermostat is defective. You can test the component for continuity, a continuous electrical path that should be present in the part. Generally, if the thermostat has no continuity then the part has failed, you can choose from a variety of multimeters to perform the test.

Step 1

Before you perform the test, make sure you shut off the power supply to the unit.

Step 2

When using an analog model first rotate the rain selection, dial to the lowest setting for ohms of resistance. Then calibrate the meter by pinching the leads together while adjusting the needle to read zero when using a digital model, again, rotate the dial to the lowest setting for ohms of resistance or resistance with a tone if your meter has this option.

Multimeter

Step 3

Next, remove the upper access panel, move the insulation out of the way and detach the protective cover.

Step 4

The upper thermostat has a reset button that can trip if the water in the tank has been overheated. This can be caused by the thermostat contacts fusing closed the thermostat being out of calibration or a shorted heating element. Reset the button if necessary, then note the orientation of the power wires and disconnect them to isolate the thermostat from the circuit.

Step 5

Now touch one lead to the left side, terminal on the reset portion of the thermostat, and the second lead to the other left side terminal, the meter reading should indicate close to zero ohms of resistance. If the component has continuity, however, if the analog meter needle does not move at all, or the digital display does not change significantly, then the thermostat has no continuity and is defective. Repeat the test on the right-side terminals.

Step 6

You should also test the lower portion of the thermostat. Touch one lead to the common terminal and the second lead to the upper heating element terminal. If the water temperature is below the designated setting, the meter should indicate close to zero ohms of resistance. Move the second lead to the lower heating element terminal and the meter should indicate no continuity. If the water temperature is above the designated setting, the reverse will be true. The lower element terminal should show continuity and the upper element terminal should not.

Next, you should test the lower thermostat.

Step 7

Make sure the power wires have been disconnected to isolate the component. Lead to one of the terminals and the second lead to the other terminal. If the water temperature is below the designated setting, the meter display should show close to zero ohms of resistance. If the water temperature is above the designated setting, the meter display should indicate no continuity and the opposite reading will mean that the thermostat is defective and will need to be replaced.

How to Test Water Heater Thermostat – Final Word

We hope this quick manual was useful and you were able to test your water heater thermostat. If you have any open questions on how to test water heater thermostat please contact us!

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