How to Test a Water Heater Thermostat

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Electricity is the lifeline of the modern world. Everything you are using today has been working on electricity in one form or another. So, it is important for you to try and figure out the working of your electric appliances. The reason being, the electric circuits are very delicate and may stop working even if a minute fault occurs. As for example, if you are using an electric water heater at home, you might find it difficult to trace the cause if its thermostat stops working.

But with some research you can learn how to test water heater thermostat. You can start with testing water heater element and then if you find it in working order, you can go ahead with the electric water heater thermostat troubleshooting. Whatever is the case, you need to learn about the basics of how a water heater works.

Structure of Water Heater:

The electric heater has a total of two thermostats, each performing distinct functions:

  • Upper thermostat makes it possible for you to have cold water supply when you turn on the tap of hot water
  • Lower Thermostat ensures that the hot water keeps coming and it does not turn cold when you turn on the hot water tap.

How to Test Water Heater Thermostat

Working of the Thermostat:

If you have a closer look at the thermostat and its working, you will come to know that it performs mainly three features, one of which is thermostat. Water heater thermostat wiring plays a crucial role in the working of the heater and therefore, you should check the circuits first.

A thermostat in the water heater helps to:

  • Produce hot water which you can consume for various purposes in your household.
  • Regulates the flow of current through to the other thermostat or a heating element.

If you have a storage tank with a capacity of at least 30 gallons, then the water heater would be having two heat elements and you will have two thermostats for each element. They work as under:

  • The upper thermostat serves as a primary thermostat and must have a high limit switch.
  • The lower thermostat on the other hand monitors the fluctuation in the temperature of the water
  • Both the thermostats do not work simultaneously.
  • The upper thermostat has a safety button which makes it stop working when the temperature of water rises above 170-degree Fahrenheit.
  • If you want to restore the settings, you should press this particular button.
  • If you want to set up the thermostat on water heater, you will have to adjust the temperatures of both thermostats at same temperature.

Test the Water Heater Thermostat

Testing the water heater thermostat involves the checking of the heating element also. Before you proceed further with the process of testing the heater thermostat, take a screwdriver and the multimeter.

  1. Start by checking the thermostat terminals for the supply of power. Read the terminal no.1 and 3 carefully, if you see the figure of 240V, it means the current is coming. Alternatively, go back to have a look at the power source to turn it on.
  2. You need to check the limit of the upper thermostat also. For this, look at the button on the thermostat.
  3. Next, you have to turn off the lower thermostat. You can do this if you rotate its dial to the zero setting. At the same time, increase the temperature on the upper thermostat in order to trace out the fault.
  4. Now, you have to put the prangs of multimeter on the Terminal no. 1 and the heating element which is blue in color. In this way, you will be able to know if the electricity is flowing between the heating element on the upper side and the blue wire or not.
  5. You should go through the reading on the multimeter. If it is 240V, it means that you are having the electric supply.
  6. Now is the turn of terminal no. 2 to be checked with the multimeter. Again, place them on the terminal no. 2 and the blue wire, you should be having a reading here also. If nothing appears, it implies that there is something wrong with the thermostat.
  7. Then you need to check the lower thermostat. For this, turn back its dial to the zero setting and at the same time, bring the other thermostat to the maximum setting.
  8. Once again, check the terminal no. 1 as well as the red wiring on the lower thermostat. Test the flow of electricity with the help of multimeter and if you have a reading 240V, it means you are a proper supply of current there.
  9. Similarly, check the terminal no. 2 and the red wiring of the same lower thermostat, in case, you do not have any figures, the thermostat of your water heater is not working well and you need to replace it with a new one.

How to Test Water Heater Thermostat

How to replace a water heater thermostat?

Once you have figured out that there is some fault with the water heater thermostat, now is the time for you to replace it. Now, here is how you can do this:

  1. First of all, power off the electric supply. Now remove the entire panel which is supposed to protect the water heater and the heating element. Use the screwdriver if there are screws. Be careful for not touching the naked wires as it may be dangerous.
  2. Now, before you pull out the faulty thermostat, you should take a picture of the circuits so that you may connect the wires in the same manner when you replace the new thermostat.
  3. Unscrew the terminals of the thermostat and remove it completely from the chamber by getting rid of the attachment clips.
  4. Now, connect the new thermostat following the connections in the picture you took earlier on and adjust the temperature on the thermostat which is normally 120-degrees Fahrenheit.
  5. Place the thermostat back in to its chamber and re-connect the wiring.
  6. Switch on the heater for 2 hours straight to check if it is working well.


So, this is how you can fix the thermostat of your water heater all by yourself. There is no need of hiring a technician. All you have to do is to follow these steps and you will be able to have hot water supply in your household in no time. This is not only going to be helpful for saving time but you will be self-sufficient also in this respect.

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