Skip to main content

Owning a home requires a lot of patience and maintenance. If you own a home, you will want to create a checklist of monthly and yearly maintenance. The various systems of your home require that you maintain them on a regular basis. HVAC, Furnace, plumbing, and electrical systems are 4 of the main areas of the home that require regular maintenance. For example, your furnace requires filter replacements and cleaning of the flame sensor. How do you clean the furnace flame sensor? Just like any maintenance of the home, there is a step-by-step process in order to clean the flame sensor.

Let’s take a look below at what is needed and the steps to clean your furnace flame sensor.

What Is A Flame Sensor?

Furnaces have some very important working parts. Most of which provide the homeowner with some peace of mind. In a furnace, there is a device called a flame sensor. Its sole purpose is to ensure that a flame is lit and to heat the gas that is fed to the unit. If there is no flame, the flame sensor will instruct the furnace to shut down. This ensures that gas isn’t backing up into the home and creating a major health and safety hazard. The flame sensor is a thin metal rod that is usually bent. It is installed inside the furnace near the front of the flame stream.

A typical furnace flame sensor.

Why Is My Flame Sensor Dirty?

Just like most appliances in the home, parts can get dirty and either break down or cause a lack of efficiency in the equipment. When using your furnace, the flame sensor can become dirty from the buildup of carbon. The smallest traces of carbon buildup will cause the flame sensor to shut the furnace down. Consider it like a smudge on a window. If the flame sensor has a smudge it cannot get a proper flame reading and will shut the furnace off. This protects the home from a buildup of gas.

What Tools Do I Need To Clean It?

When it comes to cleaning your flame sensor you will need a few tools and materials. Let’s take a look below at what those are.

  • Paper towels or a dry rag
  • Some steel wool, emery cloth, or light grit sandpaper
  • 1/4″ hex screwdriver or a wrench (This tool depends on the type of mounting hex head screw used in the unit.)

How Do I Clean The Flame Sensor?

Cleaning the furnace’s dirty flame sensor is one of the few items that does not require an HVAC expert. As the homeowner, you will be able to remove and clean the furnace flame sensor if you follow the steps below. Let’s take a look.

  1. Turn off the power – Make sure that you shut off the power to the furnace. Typically, there is a toggle switch or light switch located next to the furnace. Flip it into the off position. Additionally, you can use the circuit-breaker switch in your breaker box and simply flip it off. Also, shut off the gas.
  2. Locate the flame sensor and remove it – Typically, a flame sensor is easily accessible. You will find it located next to the burner assembly. Find the access panel to your furnace and remove the panel by sliding it open or removing the screws. Also, keep in mind that you might need to disconnect the wiring from the flame sensor. This allows you to easily remove it.
  3. Clean the flame sensor – Gently rub the flame rod sensor with your sandpaper or steel wool. You will notice the carbon buildup starts to come off the sensor rod. Check the power wire for corrosion. Once you have sanded the carbon from the flame sensor rod, wipe it down with a paper towel or clean rag. This removes the sandpaper dust and carbon particles and cleans the sensor.
  4. Reinstall the flame sensor – Once you have finished cleaning the flame sensor you will need to reinstall it. Reconnect the power wires and screw the flame sensor back into place. You will replace the flame sensor in the same manner in which you removed it.
  5. Power up – Once you have properly reinstalled the flame sensor you can turn the power to your furnace back on. If you flipped the circuit breaker, then go ahead and turn the breaker back on. The furnace will begin to cycle through its safety checks as it begins to power up. Be patient and wait to see if the system comes back online. If the furnace keeps shutting down, you will likely need to buy a new flame sensor and replace the broken flame sensor.

Other Recommended Maintenance

Now that you understand how to clean your flame sensor, it might be a good idea to read up on other reasons why your furnace might not turn on. Keep in mind that if you have cleaned the flame sensor and the furnace still won’t turn on, there could be other areas in the furnace needing fixing.

Next, while you are cleaning your furnace flame sensor, this would be a great time to change your furnace filters. Be sure to read up on where the furnace filter for your model furnace might be located.

Lastly, while you are conducting maintenance on your furnace, this would also be a good time to check on your water heater. Make sure that you understand how long your water heater takes to heat up. Knowing this allows you to determine if parts are breaking down and if something needs to be replaced.

If you cannot clean the flame sensor call on a furnace repair technician.

When Do I Call A Professional?

If you have an issue with your furnace it might be a good idea to call on your local HVAC system technician. Not only can they troubleshoot any issues that you might be having, but they can also conduct regular maintenance. Getting your furnace maintained ensures that you will have heat in the colder months. If you aren’t sure who to call, reach out to your local home inspection team. They can inspect all systems of your home to prepare you for the colder months ahead. Additionally, they can recommend a reputable HVAC repair technician to maintain your furnace.


When it comes to your furnace you will want to make sure that you maintain it on a regular basis. The last thing a homeowner would like to see is that in the coldest time of the year, their furnace malfunctions. Also, make sure to call on your local home inspection team to assess and inspect your furnace and all vital systems of your home. You would not want anything breaking down during the most weather-threatening times. Reach out to Enviroquest Home Inspections for a furnace and complete home inspections in Harrisburg, PA.

Leave a Reply