Water heater temperature sensor failure: how you can get hot water again?

The water heater has a special temperature sensor that operates on the principle of the signal switch function. It signals the gas control valve to release or block the gas supply. However, it is not uncommon for the water heater temperature sensor failure. More details about the main causes of water heater sensor failure will be discussed in this article.

water heater temperature sensor failure

The principle of operation of the water heater temperature sensor

Before proceeding with the study of water heater temperature sensor failure, you should familiarize yourself with the operation of the temperature sensor.

As soon as the element notices that the temperature drops, a signal is given to the heating element that is inside.

Next, the heating element begins to heat the water. Once you reach the desired temperature, the thermostat turns off the power.

Purpose of the thermocouple

The temperature control sensor is called a thermocouple. It controls the temperature function of the water heaters. If you plan to replace a temperature sensor attached that has stopped working, you need to familiarize yourself with the functions of a thermocouple.

The thermocouple opens the gas valve. If the control lamp goes out, the thermocouple stops supplying gas. If the thermocouple does not work, then the gas supply will not be carried out. Therefore, it is impossible to understand whether the control lamp lights up.

Therefore, you need to test the temperature sensor using a multimeter. Only after the diagnosis will you understand whether a replacement will be required.

Water heater temperature sensor failure: how you can get hot water again?

Signs of faulty temperature sensor

You can make sure that the temperature sensor is working after checking and monitoring the temperature. If it is a faulty temperature sensor, then you will notice several signs:

  1. 5 flashes. If the temperature sensor is not working, the gas water heater status indicator glows exactly 5 times.
  2. The presence of too hot water. If the water temperature is heated to a level that is impossible and unsafe to swim in it, then there is a malfunction in the operation of the thermal sensor.
  3. Cold water supply. If the water just flows, the gas water heater starts to heat up. If the temperature sensor stops working, then there is a supply of cold or barely warm water.
  4. Faulty gas control valve. Therefore, the water cannot heat up to the desired level.
  5. Replacement of the thermostat.

Fixing a malfunction of the water heater sensor

If the water heater sensor is not working, it can cause many problems in the future.

Sensor contamination

If debris begins to accumulate in the water heater, it stops working properly. Often this happens if you do not clean the temperature sensor for a long time.

Therefore, it makes sense to first find the sensor and clean it up. Then try to start the water heater again.

Starting and shutting down the water heater

If there is damage to the sensor, first turn it off and immediately start the water heater. This helps fix the clutches. Recycling the power supply will ensure the proper functioning of the water heaters.

First, you need to turn off the gas handle of the device and remove the door that is outside. Leave the device in this position for 10 minutes.

This facilitates the release of gas that has accumulated.After that, you can light the igniter, and set the gas control knob to the “Pilot” mode.

Next, you need to hold down the handle button together with the piezo igniter button. You need to hold the buttons until the sound from the clock appears. Then the indicator lights up. After that, you can set the handle to the desired position.

Water heater temperature sensor failure: how you can get hot water again?

Sensor failure

Often this happens if the sensor goes beyond the resistance limits.

Therefore, first, you have to check the water heater and check the resistance indicators.

If the indicators are out of range, a replacement should be made.

Sensor test

To work, you must arm yourself with a multimeter. However, testing may differ depending on the water heater model.

To check the sensor, you first need to get to it. To do this is quite simple. First, you need to disassemble the gas valve. After fixing the gas valve to the back panel, attach a multimeter to it.

For connection, it is better to use contact probes. Check the contacts so that they do not interfere. After that, put the probe in the central hole, and the second one should be fixed to the hole, which is on the outside.

Then proceed to read the resistance, and measure the heating temperature of the water heaters. You have to compare the data with the table from the manufacturer. If the indicators are normal, then the water heater is working correctly. The problem may lie in the malfunction of the control gas valve, and it needs to be changed.

If the indicators are not correct, then you need to change the water heater sensor itself. The detailed process will be described next.

Temperature sensor replacement: basic rules

If the sensor stops working, then you need to replace it. First, you have to prepare the tools. Wrenches of different sizes are required. Then proceed to the main stages of work.

First, you must disconnect the gas connection. To do this, the shut-off valve is turned off. After you have to disconnect the temperature battery and remove the igniter. Disconnect the gas supply valve using a 7/16″ wrench.

Then arm yourself with a ¾ inch wrench to prevent the main gas flow to the water heater. Next, remove the front door of the device. To do this, remove the two fixing screws.

Using Torx T20, you also need to unscrew 2 screws. In this case, the nuts are removed with a wrench. After unscrewing the screws, take out the burner unit. After that, you will need to move the sensor a little, remove the fasteners, and remove it. Replace immediately. Then follow all steps in reverse order.

Not a tight connection

If the sensor is loose, it will not work properly. The gas control valve will be signaled. Because of this, the water will not heat up to the desired levels.

The solution to the problem is to check the quality of the connection. If the fixation is weak, the connection will need to be tightened.


At the bottom of the tank, where the water is, calcium carbonate can accumulate. It resembles a white precipitate. If deposits accumulate, the sensor is faulty. After all, water is displaced, and the amount of hot water is negligible.

If deposits build up, the temperature change is drastic. After all, the sensitivity of the sensor deteriorates. The solution to the issue is to clean up the sediment. After, the device should work quietly.

Water heater temperature sensor failure: how you can get hot water again?

If replacing the sensor did not help: actions

If you replaced the sensor, however, the problem persists, you can use other methods to solve the problem. You can remove the burner assemblies and clean them. Soot and dirt must be removed. The burner may need to be replaced.

Examine the water tank. Remove sediment and deposits from it.

You should also check the patency of the pipes in the house. They mustn’t be clogged.

How to properly maintain a water heater?

Proper care of the device has a positive effect on its performance and durability.

Water heater insulation

If you insulate an electrically powered water heater, no heat is lost. Therefore, you can reduce the cost of heating water. Before starting work on insulation, you should study the rules and regulations that are prescribed by the manufacturer.

Otherwise, you risk losing the operating rules, as well as safety standards. It is possible that unknowingly you close the gas control panel, constipation devices, as well as main valves. There is also a risk of blocking the air valves that provide heat and draft. This causes unsafe operations.

Insulation should be placed in places where the control panel, gas valve, and regulators are located. The water heater must first be turned off so that it is safe for you to carry out all your work. As soon as the work is completed, the device should be started.

Pipe insulation

If you insulate the pipes, no heat is lost. Thanks to this, the water is several degrees hotter. Therefore, you do not have to constantly adjust the water temperature because heat compensation is not required. You can save water because you do not have to let the water drain to the desired temperature in vain.

If you are using a water heater that runs on gas, the insulation should be placed 6 inches from the chimney.

If the plumbing pipes are 8 inches or less from the vent, work with a fiberglass wrap that is 1 inch or thicker.

Cladding is prohibited. You need to fix the wrapper with wire or tape, which is made of aluminum foil.

Draining water and washing sediment

When hard water is heated, precipitation begins to stand out. They accumulate in the tank, which will deteriorate the water heater’s efficiency. After all, there is no sensitivity to water temperature changes. Deposits will accumulate on top of the heat exchange.

The device needs more time to heat up, and the operation is very noisy. Before draining the water, the water heater must be disconnected from the power supply. If the device is gas, you should set the “Pilot” mode.

Drain the water from the tank, then fill it with cold water. This keeps the sediment from mixing. Once you have drained the water, fill it with water until clean water flows through the drain hose. Close the drain and fill the tank with water. Reset the “Pilot” mode, and start the device.

Water heater temperature sensor failure: how you can get hot water again?


In the process of working with a water heater’s temperature sensor, you may encounter various issues.

How do you reset the temperature sensor on a hot water heater?

On the electrical water heater, there is a special reset button. Water heaters have a red tint and are located near the thermostat. The button may be hidden behind a metal panel and insulation. You need to find the button, hold it down, and then release it.

What does a water heater temperature sensor do?

If the water temperature drops, a signal is sent to the heating element, which is located inside the tank. This helps to get hot water. As soon as it reaches the desired temperature, the power turns off due to the thermostat. Thanks to the insulation, the water inside the tank keeps the temperature.


As you can see, errors in the operation of the water heater sensor can occur for various reasons. You must first diagnose the problem with the hot water heater, and then proceed to eliminate them.

Read About How To Replace A Water Heater Thermocouple

Robert Brooks

I have an engineering background. I have my own house, where I live with my wife and children. I want to say that the most important thing when equipping a house is to choose the right heating, ventilation, and air conditioning systems.

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