Top 7 Warning Signs of a Failing Water Heater Flame Sensor


A water heater is essential for providing consistent hot water and maintaining comfort in the home. However, when the flame sensor begins to fail, it can lead to a series of issues. If ignored, it can result in inconsistent heating, system shutdowns, and even complete failure. Identifying the signs of a malfunctioning flame sensor early is key to preventing costly repairs and ensuring smooth operation. In this article, we’ll explore the top seven warning signs of a failing water heater flame sensor.

Common Warning Signs of a Failing Water Heater Flame Sensor

Below are the most common symptoms that point to a faulty flame sensor, what causes them, and how you can fix each issue before it leads to total heater failure.

1. Water Heater Turns Off Shortly After Igniting

When your water heater turns on for a brief moment and then shuts off, the flame sensor might not be detecting the flame properly.

Signs of a Failing Flame Sensor

  • Short Ignition Cycles: The heater ignites but shuts off within seconds, failing to maintain operation.

  • No Hot Water Despite Attempting: The system turns off before adequate hot water can be produced.

  • Frequent Restarts or Ignition Attempts: The water heater repeatedly tries to ignite, but it doesn't hold the flame.

Fix: After turning off the gas and electricity, take out the flame sensor and give it a gentle cleaning with fine-grit sandpaper. Replace the sensor if the problem continues.

2. Inconsistent Hot Water Supply

An unreliable hot water supply—sometimes hot, sometimes cold—is a clear indicator of a malfunctioning flame sensor interrupting the burner operation.

Signs of a Failing Flame Sensor

  • Fluctuating Water Temperature: Water temperature changes unexpectedly between hot and cold while in use.

  • Delayed or Slow Heating: It takes an unusually long time to heat the water, or it never heats to the desired temperature.

  • Uneven Heating: You experience hot water initially, but it quickly turns cold or lukewarm during use.

Fix: Clean the flame sensor to restore proper flame detection. You might have to replace the sensor completely if that doesn't work.

3. Failure to Ignite the Burner

If your water heater clicks but never ignites, or it takes multiple attempts to start, the flame sensor might not be sending a signal to the control board.

Signs of ignition failure:

  • Clicking Without Flame: The igniter clicks repeatedly, but no flame ignites in the burner.

  • Failure to Heat After Several Attempts: The system tries multiple times but doesn’t ignite or light up the burner.

  • Error Codes Appear: The system may display "Ignition Failure" or "Flame Not Detected" on the control panel.

Fix: Inspect the flame sensor for dirt or corrosion. To get it back in working order, clean it or replace it as needed.

4. Flashing Error Codes or Warning Lights

Digital water heaters often display error codes when there’s an issue with the flame sensor or ignition system.

Signs of a Failing Flame Sensor

  • Flashing Control Panel Lights: Warning lights on the control panel indicate a failure in detecting the flame.

  • Displayed Error Codes: Error codes such as "Flame Not Detected" or "Ignition Failure" signal a malfunction.

  • System Lockouts: The heater may lock itself out, requiring a manual reset due to frequent failure to detect the flame.

Fix: Clear error codes, inspect the sensor, and clean it. If the problem continues, a replacement might be required.

5. Visible Soot or Burn Marks Near the Burner

A failing flame sensor can cause inconsistent burner operation, leading to poor combustion and soot buildup near the sensor or burner area.

Signs of a Failing Flame Sensor

  • Blackened Metal Near Burner: Soot or carbon buildup around the burner area indicates incomplete combustion.

  • Burn Marks Around Sensor: Visible scorch marks or discoloration near the flame sensor or burner.

  • Burning Smell: A strong burning odor could indicate a malfunction in the combustion process caused by the sensor's failure.

Fix: Clean the burner area thoroughly and inspect the flame sensor. Replace the sensor if necessary.

6. Excessive Clicking During Startup

Continuous clicking sounds during startup, without ignition, may suggest that the flame sensor is not properly detecting the flame.

Signs of a Failing Flame Sensor

  • Repeated Clicking Sounds: The igniter clicks multiple times without the burner igniting.

  • No Flame Despite Clicking: The system doesn’t ignite even after several attempts, leaving the heater in a perpetual clicking state.

  • Short Cycle and Shutdown: The heater attempts to ignite but shuts off before sustaining the flame.

Fix: Turn off the heater, remove and clean the flame sensor, and test if the clicking stops. Replace the sensor if cleaning doesn’t work.

7. Dirty or Corroded Flame Sensor

The flame sensor may corrode or get dusty, making it unable to detect the flame accurately over time.

Signs of a Failing Flame Sensor

  • Visible Dirt or Soot: The sensor is covered with carbon buildup or dirt, affecting its functionality.

  • Rust or Corrosion on the Sensor: Rusty or corroded sensor surfaces may prevent proper detection of the flame.

  • Failure to Detect Flame: The sensor doesn’t signal the system even though the flame is present.

Fix: Switch off the gas and electricity, take out the sensor, and use fine-grit sandpaper to clean it. If the corrosion is severe, replacing the sensor may be the only option.

Preventive Tips to Avoid Flame Sensor Issues

Keeping your water heater’s flame sensor in good condition helps maintain consistent hot water and system safety. Follow these few quick maintenance tips:

  • For every 6–12 months. Clean the flame sensor

  • Replace the sensor every 3–5 years, depending on use and model.

  • Keep the burner area free of dust, soot, and moisture.

  • Make an appointment for a professional water heater inspection each year.

A failing flame sensor isn’t something to ignore. Even while it could begin with sporadic problems, if ignored, it might result in irregular hot water, frequent restarts, and even total system failure. By understanding the signs and addressing them early, you’ll save time and money while ensuring your water heater works efficiently.

Tired of dealing with water heater issues? PartsHnC offers high-quality components like flame sensors, control boards, thermostats, and gas valves to keep your system running smoothly.

FAQs

What happens when a flame sensor goes bad?


When a flame sensor goes bad, it fails to detect the flame properly, causing the water heater to shut off or fail to ignite. This leads to inconsistent heating or no hot water at all.

Why does my heater flame keep going out?

A heater flame may keep going out due to a faulty flame sensor that can't detect the flame, dirt buildup on the sensor, or issues with the gas supply or burner. Regular maintenance can help resolve these issues.
Location: United States

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