Water Heater Temperature Sensor Failure: Understanding and Fixing the Issue


Water heaters are essential appliances in our homes, providing us with hot water for various purposes. However, like any other mechanical device, they can experience issues over time. One common problem that users may encounter is water heater temperature sensor failure.

In this article, we will explore the reasons behind this failure, signs that indicate a faulty temperature sensor, and effective ways to fix the problem. We will also cover specific scenarios, such as the failure of Honeywell water heater temperature sensors, and how to reset and replace a malfunctioning temperature sensor. Let’s dive in!

Note: You can read our blog on the Working of Different types of Water Heaters and specifically How Does Electric Water Heater Work?

1. Reasons for Water Heater Temperature Sensor Failure

Before we delve into the signs and solutions, it’s crucial to understand why water heater temperature sensors may fail. Several factors can contribute to this problem, including:

– Corrosion and Mineral Buildup

Water heaters deal with water constantly, and over time, minerals and sediments from the water can accumulate on the temperature sensor. This buildup can hinder the sensor’s ability to accurately measure the water temperature.

– Electrical Issues

Temperature sensors rely on electrical components to function correctly. Electrical problems, such as short circuits or damaged wires, can disrupt the sensor’s performance.

– Sensor Age and Wear

Like all mechanical components, temperature sensors have a limited lifespan. As they age, their efficiency may decrease, leading to failure.

– Manufacturing Defects

In rare cases, a manufacturing defect can cause a temperature sensor to malfunction prematurely.

2. Signs of Water Heater Temperature Sensor Failure

Detecting a failing temperature sensor early can save you from more significant problems later on. Keep an eye out for the following signs:

– Inconsistent Water Temperature

If you notice that your water heater is producing water at erratic temperatures, it could indicate a faulty temperature sensor.

– No Hot Water

A malfunctioning temperature sensor might cause the water heater to stop producing hot water altogether.

– Constant Heating Element Activation

A faulty sensor may continuously signal the heating element to stay on, resulting in excessively hot water and potential damage to the unit.

– Error Codes or Warning Lights

Modern water heaters often have built-in error codes or warning lights that may indicate a temperature sensor problem.

3. How to Fix Water Heater Temperature Sensor Failure

Fixing a water heater temperature sensor failure may vary depending on the specific issue. Here are some general steps to troubleshoot and address the problem:

Step 1: Turn Off the Power

Before attempting any repairs, ensure the power supply to the water heater is switched off to avoid electrical hazards.

Step 2: Check for Mineral Buildup

Inspect the temperature sensor for mineral deposits or corrosion. If you find any, carefully clean the sensor using a soft brush and a descaling agent.

Step 3: Examine Electrical Connections

Inspect the wiring connected to the temperature sensor. If you notice any loose or damaged connections, consider repairing or replacing them.

Step 4: Test the Sensor

Use a multimeter to check the resistance of the temperature sensor. Compare the reading with the manufacturer’s specifications to determine if it’s within the acceptable range.

Step 5: Replace the Sensor

If the sensor fails the resistance test or shows signs of physical damage, it’s time to replace it with a new, compatible sensor.

4. Checking the Water Heater Temperature Sensor

To ensure your water heater’s temperature sensor is functioning correctly, follow these steps to perform a thorough check:

Step 1: Access the Sensor

Locate the temperature sensor, which is usually positioned near the bottom of the water heater tank, and gain access to it.

Step 2: Disconnect Wires

Carefully disconnect the wires connected to the sensor. Remember to turn off the power supply first.

Step 3: Measure Resistance

Using a multimeter, measure the resistance of the sensor. Compare the reading with the manufacturer’s specifications to verify its accuracy.

Step 4: Check for Damage

Inspect the sensor for any physical damage or signs of corrosion that could affect its performance.

5. Honeywell Water Heater Temperature Sensor Failure

Honeywell is a reputable brand known for producing high-quality products, but even their water heater temperature sensors can encounter issues. If you own a Honeywell water heater and suspect a temperature sensor failure, follow the steps mentioned earlier to diagnose and fix the problem. Refer to the manufacturer’s manual for specific guidance related to your Honeywell model.

6. How Do You Reset the Temperature Sensor on a Hot Water Heater?

If you believe that your water heater’s temperature sensor is not functioning correctly, you may attempt to reset it before considering a replacement. Keep in mind that not all water heaters have a reset option, so consult your unit’s manual for precise instructions. In general, the reset process involves:

  1. Turn off the power to the water heater.
  2. Locate the reset button, which is often near the temperature control panel.
  3. Press and hold the reset button for a few seconds.
  4. Restore power to the water heater and check if the sensor starts working correctly.

7. How Do You Fix a Temperature Sensor That Is Failing?

To address a failing temperature sensor, several steps can be taken to troubleshoot and resolve the issue effectively. Here’s a comprehensive guide on how to fix a temperature sensor that is showing signs of failure:

  1. Turn Off the Power: As a safety precaution, start by turning off the power supply to the water heater. This step ensures there are no electrical hazards while working on the sensor.
  2. Inspect for Visible Damage: Carefully examine the temperature sensor for any visible damage or signs of corrosion. Physical issues could be contributing to its malfunction.
  3. Check Electrical Connections: Inspect the wiring and electrical connections associated with the temperature sensor. Loose or damaged connections can interfere with its proper functioning.
  4. Test the Sensor’s Resistance: Use a multimeter to measure the resistance of the temperature sensor. Compare the reading with the manufacturer’s specifications to determine if it falls within the acceptable range.
  5. Clean the Sensor: If you notice any mineral buildup or debris on the sensor, gently clean it using a soft brush and a descaling agent. This can restore its accuracy in measuring water temperature.
  6. Reset the Sensor (if applicable): Depending on your water heater model, there might be a reset option for the temperature sensor. Follow the manufacturer’s instructions to perform a reset.
  7. Replace the Sensor (if necessary): If the temperature sensor fails the resistance test, exhibits physical damage, or cleaning doesn’t improve its performance, it’s time to replace it. Purchase a compatible replacement sensor from a trusted supplier.

8. How Much Does It Cost to Replace Temperature Sensor on Water Heater?

The cost of replacing a water heater temperature sensor can vary depending on factors such as the brand, model, and location of the water heater. In general, the price of the sensor itself is relatively affordable, ranging from $20 to $50.

However, if you’re not confident in your DIY skills, hiring a professional plumber or technician to replace the sensor may add to the total cost.

Key Takeaways

  • A water heater temperature sensor failure can lead to inconsistent hot water supply or no hot water at all.
  • Regular maintenance and cleaning can prevent mineral buildup, which often contributes to sensor failure.
  • Performing routine checks using a multimeter can help diagnose sensor issues accurately.
  • Always follow safety precautions and turn off the power before attempting any repairs on your water heater.

Some Facts About Water Heater Temperature Sensor Failure

✅ Temperature sensor failure can be caused by corrosion, electrical problems, wear over time, or manufacturing defects.

✅ Signs of a failing temperature sensor include erratic water temperature, no hot water, continuous heating element activation, and error codes or warning lights.

✅ Troubleshooting a temperature sensor involves checking for mineral buildup, inspecting electrical connections, and testing the sensor’s resistance.

✅ Resetting the temperature sensor is possible on some water heaters, but not all models have this feature. Consult your unit’s manual for specific instructions.

✅ The cost of replacing a water heater temperature sensor typically ranges from $20 to $50, excluding any additional labor charges if you hire a professional.

Expert Opinion

As an experienced MEP Engineer, I recommend homeowners to perform regular maintenance on their water heaters, including checking and cleaning the temperature sensor. Timely action can prevent issues and ensure the efficient functioning of your water heater for years to come.

If you encounter any problems beyond your expertise, don’t hesitate to seek help from a licensed professional to avoid costly mistakes and ensure your safety.


What are the common reasons for water heater temperature sensor failure?

Water heater temperature sensors may fail due to corrosion, mineral buildup, electrical issues, sensor age, or manufacturing defects.

How can I detect a failing temperature sensor in my water heater?

Look for signs such as inconsistent water temperature, lack of hot water, constant heating element activation, or error codes/warning lights on the unit.

Can I reset the temperature sensor on my hot water heater?

Some water heaters have a reset option. Refer to your unit’s manual for specific instructions on how to reset the temperature sensor.

Is it necessary to hire a professional to fix a failing temperature sensor?

While some issues can be resolved through DIY troubleshooting, if you are uncertain or uncomfortable with the repairs, it’s best to hire a licensed professional for safety and accuracy.

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