How To Test Water Heater Thermostat

Most of the water heater contains a thermostat to maintain a specific temperature. It allows the water heater to power on/off automatically while it gains the appointed heating level. However, if the thermostat has defected, the heater does not work correctly. Either the heater always remains on, or it might not get power at all. If you face such an issue with your water heater,  it indicates that the thermostat may have defected. However, there’s some effortless way to test & repair. Just follow the steps below. Please remind one thing, do not play with electricity. Make sure you have ensured enough safety, How To Test Water Heater Thermostat.

First Scenario: Water heater is not getting power. Alternatively, water is not heating at all.

How To Test Water Heater Thermostat This case might happen for the defected thermostat. Although most of the cases this scenario occurs for the power supply problems. So at first make sure your power cord is okay. Check your heater’s power connecting point. You may insert the power pluck and hold a Tester at the heater’s connecting point to check if the power is available. If the connection point does not get electricity, then change the power cable and start your heater. If the power supply is okay, then manage a series lamp or multimeter.

Using Series Lamp:

Hold the A and B point of the series lamp with the heater’s pluck. If the thermostat has not defected, then the bulb will light. Otherways the bulb won’t light. It’s the easiest method to test your thermostat for the first scenario.

Using a Multimeter:

Set the multimeter at the lowest ohm point. Then touch both pins together, the reading will show ZERO. No matter the meter is digital or analog. If your meter is analog, then tune the indicator at Zero while touching both pins ends. Then contact the multimeter’s pin ends with the two ends of heater’s power plug. If the thermostat has not defected, a change of multimeter reading will happen. If no change occurs on the multimeter display, it means that your heater’s thermostat has defected.

Second scenario: The heater always remains on and never off in spite of raising a specific temperature.

Remaining always ON is the most common issue with electric water heaters. In this case, testing the thermostat is a little bit of a technical task but not hard at all. Once again, safety first. Do not play with electricity. Make sure you have disconnected the power plug. Now you have to follow the steps carefully.

  1. Remove the upper panel cover & detach the protective cover. You will find the thermostat the same as the image below. The upper thermostat has a reset button that might trip sometimes. It can cause because of
  2. The thermostat Contacts fusing closed.
  3. Thermostat out of calibration.
  4. Shorted heating element.

Reset that button if needed. Then follow further steps.

Note: Set the multimeter at the lowest ohm point as I described above. If that is analog, then set them lowest ohm point and contact both pin ends together and tunes the indicator at the Zero point.

Test 1:

Connect the multimeter pin ends on point A & B, as shown in the picture below. If your multimeter points near Zero then the thermostat is Okay. Unless it happens, the thermostat has defected.

Test 2:

 Connect the multimeter pin ends on point C & D, as shown in the picture below. If your multimeter points near Zero then the thermostat is Okay. Unless it happens, the thermostat has defected.

Test 3:

 Connect the multimeter pin ends on point 1 & 2, as shown in the picture below. If the water is cold, the multimeter will point near Zero. If the water is hot enough at appointed temperature, the meter won’t show reading. If the opposite thing happens, that means your thermostat has defected.

Test 4: 

Connect the multimeter pin ends on point 1 & 3, as shown in the picture below. If the water is hot enough at appointed temperature, the multimeter will point near Zero. If the water temperature is cold, then the meter won’t show reading. If the opposite thing happens, that means your thermostat has defected.

Following these steps, you may identify very quickly if your thermostat has defected.  Now time to take action to fix the problem. It is better to replace the thermostat with a new one. the solar pool heater is the best pool heater for your indoor or outdoor swimming pool.