Your furnace’s flame sensor is a critical component that ensures the safe and efficient operation of your heating system. A dirty flame sensor can lead to a variety of problems, including a flickering flame, ignition failure, and even a complete furnace shutdown. Cleaning the flame sensor is a simple task that can be completed in a few minutes, and it can help to prevent these problems from occurring.
The first step is to turn off the power to your furnace. This can be done by flipping the circuit breaker or pulling the fuse that supplies power to the furnace. Once the power is off, you can remove the access panel to the furnace. The access panel is typically located on the front or side of the furnace. Once the access panel is removed, you will be able to see the flame sensor. The flame sensor is a small, metal rod that is located near the burner. It is typically held in place by a single screw.
To clean the flame sensor, simply use a soft cloth or brush to remove any dirt or debris that has accumulated on it. Be careful not to damage the flame sensor, as this could cause it to malfunction. Once the flame sensor is clean, reinstall it and tighten the screw. Then, replace the access panel and turn the power back on to the furnace. Your furnace should now be operating properly again.
Understanding the Furnace Flame Sensor
The furnace flame sensor is a critical component of your furnace, responsible for detecting the presence of a flame and ensuring safe and efficient operation. Its primary function is to ensure that the furnace does not operate without a lit flame, preventing potential gas leaks and hazardous situations.
The flame sensor operates on the principle of flame rectification. It consists of a metal rod or probe that extends into the burner assembly. When the burner is lit, the flame ionizes the air between the probe and the burner ground, creating a small electrical current. This current is detected by the flame sensor and signals the furnace control board to keep the gas valve open and continue heating.
In the absence of a flame, the ionization process does not occur, and the current flow is interrupted. The flame sensor detects this lack of current and sends a signal to the control board. The board then shuts off the gas supply, preventing the furnace from operating without a flame.
Here are the key functions of a furnace flame sensor:
- Detects the presence of a flame: Ensures that the furnace only operates when a flame is present, preventing gas leaks and potential hazards.
- Monitors flame stability: Detects any disruptions or fluctuations in the flame, ensuring efficient and safe operation.
- Communicates with the control board: Sends signals to the furnace control board regarding the presence or absence of a flame, allowing the board to adjust the gas flow and ensure proper operation.
Symptoms of a Dirty Flame Sensor
A dirty flame sensor can cause a variety of problems with your furnace, including:
- Furnace won’t start. The flame sensor is responsible for detecting the presence of a flame in the furnace. If the sensor is dirty, it may not be able to detect the flame, which will prevent the furnace from starting.
- Furnace cycles on and off. A dirty flame sensor can cause the furnace to cycle on and off repeatedly. This is because the sensor is detecting the flame intermittently, which causes the furnace to shut off and then restart.
- Furnace produces yellow or orange flames. A dirty flame sensor can cause the furnace to produce yellow or orange flames. This is because the sensor is not detecting the flame properly, which causes the furnace to burn fuel inefficiently.
- Furnace produces a sooty smell. A dirty flame sensor can cause the furnace to produce a sooty smell. This is because the sensor is not detecting the flame properly, which causes the furnace to burn fuel inefficiently.
Causes of a Dirty Flame Sensor
The most common cause of a dirty flame sensor is dust and dirt. Dust and dirt can accumulate on the sensor over time, which can prevent it from detecting the flame properly. Other causes of a dirty flame sensor include:
- Lint. Lint from clothing and other fabrics can accumulate on the flame sensor.
- Pet hair. Pet hair can also accumulate on the flame sensor.
- Rust. Rust can form on the flame sensor if it is exposed to moisture.
- Corrosion. Corrosion can also form on the flame sensor if it is exposed to chemicals.
Safety Precautions
Inspecting and cleaning the flame sensor is a crucial maintenance task that requires proper safety measures. Before proceeding, ensure you have the necessary tools and knowledge to avoid any potential hazards. Here are some essential precautions to observe:
Shut Off Gas and Electricity
Turn off the gas supply to the furnace at the main valve. Additionally, disconnect the unit from the electrical power source by switching off the circuit breaker or removing the fuse. This will prevent any accidental ignition or electrical shocks during the cleaning process.
Wear Protective Gear
It’s advisable to wear protective gloves to protect your hands from any sharp edges or exposed metal components. If possible, wear safety glasses to shield your eyes from any dust particles that may be dislodged during the cleaning process.
Allow the Furnace to Cool
Before starting the inspection and cleaning, allow the furnace to cool completely. The internal components may be extremely hot, and attempting to work on a heated unit can result in burns or other injuries. Allow ample time for the unit to dissipate heat before proceeding.
Cleaning the Flame Sensor with Sandpaper
Cleaning the flame sensor with sandpaper is a relatively simple and inexpensive method that can be used to restore the sensor’s functionality. Follow these steps carefully to ensure a thorough cleaning:
- Gather your materials. You will need a piece of fine-grit sandpaper (220-grit or higher), a screwdriver, and a clean cloth.
- Disconnect the furnace. Turn off the power to the furnace and unplug it from the outlet.
- Locate the flame sensor. The flame sensor is typically located near the burner assembly. It is a small, cylindrical device with a wire lead attached to it.
- Remove the flame sensor. Use a screwdriver to loosen the screw that holds the flame sensor in place. Carefully pull the sensor out of its housing, taking care not to damage the wire lead.
5. **Reinstall the flame sensor.** Insert the flame sensor back into its housing and tighten the screw to secure it.
6. **Reconnect the furnace.** Plug the furnace back into the outlet and turn the power back on.
Cleaning the Flame Sensor with a Wire Brush
Perhaps the most basic of the cleaning methods for furnace flame sensors involves the use of a wire brush. A wire brush is a handy tool that is designed to remove dirt and debris from various surfaces, and it can be just as effective at cleaning a flame sensor as it is at cleaning other surfaces.
To clean a flame sensor with a wire brush, you will need to remove it from the furnace. To do this, first turn off the power to the furnace. There will be a switch or circuit breaker that controls the power to the furnace. Flip the switch or turn off the circuit breaker. Next, remove the access panel to the furnace. This panel is usually located on the front or side of the furnace. Once you have removed the access panel, you will be able to access the flame sensor.
The flame sensor will be attached to the burner assembly with a screw. Use a screwdriver to remove the screw, and then carefully pull the flame sensor out of the burner assembly.
Once you have removed the flame sensor, you can begin cleaning it with the wire brush. Gently brush the bristles of the wire brush over the surface of the flame sensor, removing any dirt or debris that has accumulated on the surface.
Be sure to pay special attention to the tip of the flame sensor, as this is the part of the sensor that is most likely to become dirty. Once you have cleaned the flame sensor, use a damp cloth to wipe away any remaining dirt or debris. Allow the flame sensor to dry completely before reinstalling it in the furnace.
Resetting the Furnace
Once the flame sensor has been cleaned, it’s important to reset the furnace to ensure proper operation. Here’s a detailed guide on resetting your furnace:
1. Turn Off the Power
Locate the electrical panel and switch off the circuit breaker or fuse that supplies power to the furnace. This will prevent any electrical hazards during the reset process.
2. Wait for the Furnace to Cool
Allow the furnace to cool down completely. This may take several minutes, depending on how long it was running before the reset.
3. Remove the Furnace Door
Locate the furnace door on the front or side of the unit and open it carefully. You may need to remove a few screws or bolts to detach the door.
4. Locate the Reset Button
Inside the furnace, find the reset button. It’s usually a small, red button located near the flame sensor or on the control board.
5. Press and Hold the Reset Button
Press and hold the reset button for 5-10 seconds. You may hear a clicking sound or see a light flash to indicate that the furnace has been reset.
6. Detailed Guide to Pressing and Holding the Reset Button
Depending on the specific furnace model, there may be various ways to press and hold the reset button. Here are some common scenarios:
| Scenario | Instructions |
|---|---|
| Separate Reset Button | Locate a small, independent reset button and press and hold it for 5-10 seconds. |
| Combined Reset Switch | Find a switch that combines the power switch and reset button. Turn the switch to the “Reset” position and hold it there for 5-10 seconds. |
| Push-and-Release Reset | Locate a button or switch that requires you to press and quickly release it multiple times in a row (e.g., 3-5 times rapidly). |
Preventing Future Flame Sensor Issues
By taking a few preventative measures, you can help reduce the frequency of flame sensor issues and extend the life of your furnace. Here are some suggestions:
1. Keep Your Furnace Filter Clean
A dirty furnace filter can restrict airflow and cause the flame sensor to become dirty. Clean or replace your furnace filter every month during the heating season.
2. Use High-Quality Fuel
Using low-quality fuel can produce soot and other contaminants that can foul the flame sensor. Use high-quality fuel that meets the manufacturer’s specifications.
3. Vent Your Furnace Properly
A properly vented furnace will help prevent combustion gases from accumulating in the furnace cabinet and fouling the flame sensor. Make sure the furnace vent is clear and unobstructed.
4. Check Your Burner Assembly Annually
Over time, the burner assembly can become misaligned or damaged. A misaligned or damaged burner assembly can cause the flame to impinge on the flame sensor, which can foul the sensor.
5. Use a Flame Sensor Shield
A flame sensor shield can help protect the flame sensor from heat and dirt. Flame sensor shields are available at most hardware stores.
6. Clean the Flame Sensor Regularly
Even with preventative measures, the flame sensor will eventually become dirty. Clean the flame sensor according to the manufacturer’s instructions. Most manufacturers recommend cleaning the flame sensor once per year.
7. Regular Maintenance
The best way to prevent future flame sensor issues is to have your furnace regularly maintained by a qualified HVAC technician. A qualified technician can inspect the furnace, clean the flame sensor, and make sure the furnace is operating safely and efficiently.
| Task | Frequency |
|---|---|
| Check furnace filter | Monthly |
| Clean flame sensor | Annually |
| Burner assembly inspection | Annually |
| Full furnace maintenance | Every 1-2 years |
Troubleshooting Common Problems
1. Furnace Not Igniting
If your furnace is not igniting, the flame sensor may be dirty or damaged. Try cleaning the flame sensor with a soft brush or vacuum cleaner. If it is damaged, it will need to be replaced.
2. Furnace Cycling On and Off
If your furnace is cycling on and off frequently, the flame sensor may be loose or misaligned. Check the flame sensor to make sure it is securely fastened and that the tip is positioned correctly in the flame.
3. Furnace Blower Running Constantly
If your furnace blower is running constantly, even when the furnace is not heating, the flame sensor may be malfunctioning. Replace the flame sensor.
4. Furnace Overheating
If your furnace is overheating, the flame sensor may be detecting a false flame. This can cause the furnace to run continuously, which can lead to overheating. Clean the flame sensor or replace it if necessary.
5. Furnace Not Responding to Thermostat
If your furnace is not responding to the thermostat, the flame sensor may be faulty. Check the flame sensor and replace it if necessary.
6. Furnace Producing Soot
If your furnace is producing soot, the flame sensor may be dirty or damaged. Clean the flame sensor or replace it if necessary.
7. Furnace Not Heating Evenly
If your furnace is not heating evenly, the flame sensor may be misaligned. Check the flame sensor and adjust it so that the tip is positioned correctly in the flame.
8. Flame Sensor Adjustment
The flame sensor should be positioned so that the tip is in the center of the flame. It should not be touching the flame or the burner. The flame sensor should be angled slightly downward so that it can detect the flame correctly. You can adjust the flame sensor by carefully bending it with a screwdriver or pliers.
| Flame Sensor Position | Result |
|---|---|
| Too high | Furnace may not ignite or may produce soot |
| Too low | Furnace may cycle on and off frequently or may not heat evenly |
| Too forward | Furnace may produce soot or may not heat evenly |
| Too far back | Furnace may not ignite or may cycle on and off frequently |
Professional Furnace Maintenance
Step 1: Safety Precautions
* Turn off the furnace’s power supply at the circuit breaker or fuse box.
* Allow the furnace to cool down completely before touching any components.
Step 2: Remove Furnace Cover
* Locate the access panel on the furnace’s exterior and remove it.
Step 3: Identify Flame Sensor
* The flame sensor typically looks like a small metal rod with a shiny tip.
* It is usually located near the gas burner, where the flame ignites.
Step 4: Disconnect Sensor
* Carefully disconnect the wire harness from the flame sensor.
Step 5: Inspect Sensor Tip
* Check the tip of the sensor for any dirt, dust, or corrosion.
* If the tip is dirty, proceed with cleaning.
Step 6: Use Soft Brush
* Gently brush away any loose debris from the sensor tip using a soft brush, such as a toothbrush.
* Avoid using abrasive materials that could damage the sensor.
Step 7: Use Emery Cloth
* If the sensor tip is severely soiled, use fine-grit emery cloth to lightly polish the surface.
* Be careful not to remove any of the metal from the sensor.
Step 8: Clean Sensor Body
* Wipe down the sensor body with a clean cloth to remove any additional debris.
* Ensure that the wire harness and terminals are also clean.
Step 9: Corrosion Removal and Reassembly
* If the sensor is corroded, use a cotton swab dipped in rubbing alcohol to dissolve the corrosion.
* Once the sensor is clean, reconnect the wire harness and carefully slide it back into place.
* Reinstall the furnace cover and restore the power supply.
Step 10: Test Flame Sensor
* Turn on the furnace and observe the flame sensor.
* The sensor should glow bright red when the furnace is operating properly.
* If the sensor does not glow, there may be a problem with the furnace and professional assistance should be sought.
Troubleshooting Flame Sensor Issues
The following table lists common flame sensor issues and their potential causes:
| Issue | Potential Cause |
|---|---|
| Sensor not glowing | – Malfunctioning sensor – Defective wire harness – Furnace malfunction |
| Sensor glows intermittently | – Dirty or corroded sensor – Loose wire connections – Weak flame |
| Sensor glows too hot | – Fuel pressure too high – Burners misaligned – Flame sensor too close to burners |
Step 1: Safety First
Remember to turn off the furnace and main gas supply before cleaning the flame sensor. Otherwise, you may accidentally ignite the furnace or damage other components.
Step 2: Locate the Flame Sensor
The flame sensor is a small metallic rod usually located near the burner assembly. It has a pointed tip that detects the flame.
Step 3: Remove the Flame Sensor
Locate the screw or clip that secures the flame sensor in place. Carefully remove the sensor, taking care not to damage the wires attached to it.
Step 4: Clean the Flame Sensor
Use a soft cloth or fine-grit sandpaper to gently remove any dirt, soot, or corrosion from the tip of the flame sensor. Avoid using abrasive cleaners or solvents.
Step 5: Bend the Flame Sensor
If the flame sensor is bent or damaged, carefully bend it back into a straight position. This will ensure it is properly positioned to detect the flame.
Step 6: Reinstall the Flame Sensor
Carefully reinsert the flame sensor into its holder and secure it with the screw or clip you removed earlier. Make sure it is securely fastened.
Step 7: Perform a Test Run
Turn on the furnace and observe the flame. If the flame is consistent and the furnace runs smoothly, the cleaning process was successful.
Step 8: Troubleshooting
If the furnace does not ignite or operates erratically after cleaning the flame sensor, there may be other issues. Check the gas supply, ignition system, and furnace filter.
Step 9: Regular Maintenance
Regularly cleaning the flame sensor can prevent furnace problems and improve efficiency. Aim to clean it at least once a year, or more frequently if your furnace is heavily used.
Step 10: Additional Tips
Here are some additional tips for cleaning the furnace flame sensor:
- Avoid using a vacuum cleaner, as it may damage the sensor.
- If the flame sensor is badly damaged or corroded, replace it with a new one.
- If you are uncomfortable performing the cleaning yourself, contact a qualified HVAC technician.
- Turn off the power to the furnace
- Remove the access panel to the furnace
- Locate the flame sensor. It is typically a small metal rod located near the burner assembly.
- Gently brush the flame sensor with a soft cloth or a toothbrush to remove any dirt or debris.
- Replace the access panel and turn on the power to the furnace.
- The furnace won’t start or ignite
- The furnace turns off prematurely
- The furnace cycles on and off repeatedly
- The flame in the furnace is weak or flickering
- The furnace produces soot or smoke
How to Clean a Furnace Flame Sensor
A clean flame sensor is essential for the safe and efficient operation of your furnace. When the sensor is dirty, it can prevent the furnace from igniting or may cause it to turn off prematurely. Cleaning the sensor is a simple and inexpensive task that can be completed in a few minutes. Here are the steps on how to clean a furnace flame sensor:
People Also Ask
What are the signs of a dirty flame sensor?
The signs of a dirty flame sensor include:
How often should I clean the flame sensor?
It is recommended to clean the flame sensor annually, or more often if you live in a dusty area or if your furnace is used frequently.
Can I clean the flame sensor with sandpaper?
No, you should not clean the flame sensor with sandpaper. Sandpaper can damage the sensor and make it less effective.
