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How To Clean a Furnace Flame Sensor?


Furnace is one of the useful HVAC appliances that we can use for our comfort on regular basis. Because the furnace works on flammable gas, we need to take care of it properly. In the Furnace, a flame sensor is an important component that prevents the system from overheating, exploding, etc. So, cleaning a furnace flame sensor regularly is very essential. From this post, you  can learn how to clean a flame sensor and make your task easier.

How to Clean a Furnace Flame Sensor?

The most important thing that needs to be cleaned by the house owners in their furnace systems is a furnace flame sensor.

If your furnace starts but stops suddenly after that, then more likely there is a problem with the flame sensor, and it needs to be cleaned.

It is a simple thing to do furnace flame sensor cleaning even to people who don’t have any technical knowledge.

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How does a flame sensor work?

Generally, gas-fueled furnaces are very safe and efficient heating systems, but without a working flame sensor, they are a potential disaster.

The flame sensor is a thin rod fixed in front of a flame jet. As the current passes through the rod, it can detect the temperature rise when the jet is ignited.

When there is gas flowing without the flame, the gas may accumulate and become a problem. We don’t want that to happen. So we use flame sensors to detect the presence of a flame. In case there is no flame, then there is safety automation which turns off the gas flow.

The continuous flame may cause the deposition of carbon on the flame sensor rod. The more the carbon buildup, the more the time the sensor takes to detect the flame. If the sensor fails to detect the flame, it turns the system off. So, that’s why the sensor needs to be cleaned regularly.

Things needed to clean a furnace flame sensor.

1. Hex driver - It is used to remove the panel and access the flame sensor. It will be helpful to have the whole set of them as the size of the screws vary between manufacturers.

2. Wire wool and sandpaper - They are used to scrape off the carbon deposit on the sensor rod.

3. Microfiber rags - we should use microfibers to clean the rod instead of paper or cloth as they deposit fibers on the rod and burn after re-installation, making the rod dirty again depositing carbon.

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Procedure to clean a furnace flame sensor

Step 1: Switch off the furnace

Stop the furnace if it is in a working condition by switching it off.

If the furnace works on a thermostat or a timer, it may restart while you are working with it. That’s why you should not only switch off the furnace but you should also disconnect the power supply to the furnace at circuit breaker.

It's always better to read the instructions in the manufacturer’s manual before you start the job.

Step 2: Detach the flame sensor

With the hex driver, unscrew the screws of the outer panel to get to the sensor. Then remove the sensor from its fixed position.

Even after the removal of screws, the sensor probably is attached to a wire. If the wire is too short, try to remove it if possible, for whole access of the sensor rod to clean.

Step 3: Cleaning the sensor

After the successful removal of the sensor from the furnace, you should assess the amount of carbon buildup on the rod.

The bottom part of the rod is made of porcelain, which is delicate, so you should better handle it consciously!

Now you can start rubbing the sensor rod with the sandpaper to remove the carbon. Continue to rub until you see the metal showing out and stop, as we need not scrape the metal material.

After the carbon is removed, wipe out the remaining dust with the microfiber rag.

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Step 4: Reassemble

As your flame sensor is good to get into the furnace you can start fixing it back. Plug the wire of the sensor back and fix the screws.

After fixing the sensor, fix the outer panel that we removed earlier. But remember not to over-tighten the screws as there is a chance to damage them. Just leave them a little over the finger tightness.

Step 5: Test the furnace

Now, you can plug in the power supply and do the necessary checks and switch on the system. Some systems may take time to start after a period of being switched off, no need to get panic!

Once it starts, check whether it is maintaining the temperatures according to your adjustment. Then you will know your flame sensor’s working status.

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So, this is the proper way to clean a furnace flame sensor. It is always better to clean the flame sensor and other important parts of your furnace at regular intervals, to ensure the safety and efficiency of the furnace. If you have any further queries on how to clean the furnace flame sensor, read the user’s manual provided by the manufacturer.


Related Content:

 1. Williams Monterey Wall Furnace Installation 2. Lennox Furnace Troubleshooting

3. Carrier Furnace Troubleshooting  4. Rheem Furnace Troubleshooting and Error Codes


About the Author


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He is good at writing content for E-Commerce websites related to Restaurant Equipment Parts, Appliance Parts, Food Service Parts, HVAC Parts, etc.

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