September 26, 2023


New Estate

Easy methods to Clear a Furnace Flame Sensor in 5 Straightforward Steps!

8 min read

🔥 Why Does Your Furnace Maintain Shutting Off?

One of the widespread signs of furnace failure is brief biking.

For those who have been sitting in entrance of your furnace watching it, the furnace inducer motor would begin to run, then the ignitor would both glow orange or begin sparking, then the fuel valve opens, the flame lights, the sensor detects the pilot flame (or doesn’t), after which the primary burners mild.

If every part above occurs besides the primary burner doesn’t mild up, you probably have a foul or soiled flame sensor.

Due to this fact, you’ll both want to put in a brand new flame sensor otherwise you’ll want to scrub the furnace flame sensor.

🛑 Most repairs like this are carried out by knowledgeable HVAC service restore technician, however in case you have the instruments and the arrogance to do that safely your self, then this text will stroll you thru each step of furnace flame sensor cleansing.

🔥 What’s a Furnace Flame Sensor, and How Does it Work?

Furnace Flame Sensor

Furnace flame sensors, or flame sensors usually, are normally made up of a skinny metallic rod working right into a ceramic tube (a few half inch in diameter) with one electrical wire popping out the opposite finish, which sends the flame sign to the fuel furnace management board.

The furnace flame sensor is normally positioned on the left facet of the burner meeting, with the skinny metallic rod positioned within the flame path.

When the fuel valve opens and the flame burns, it heats the flame rod, which acts as a security function by telling the management board whether or not it senses the flame or not.

This fashion, if the Sizzling Floor Ignitor or Spark Ignitor didn’t mild the flame, you wouldn’t have fuel buildup in your furnace as a result of the circuit board would mechanically shut the fuel valve.

Most gas-burning home equipment will try and mild the flame thrice earlier than locking out the furnace.

If this occurs, you possibly can cycle the facility to the furnace, however this gained’t repair the issue; it solely permits you extra time to troubleshoot the difficulty.

🔥 What Causes a Soiled Flame Sensor?

The flame sensor is at all times within the path of the furnace flame, which is a carbon-based gasoline, and when fossil fuels burn, they’ll depart a carbon residue on something of their path.

As this residue builds up, it simulates insulation which restricts the sign from the flame sensor to the furnace security controls.

Most of the time, flame sensors are simply soiled and haven’t fully failed.

So, earlier than you exit and purchase a brand new flame sensor in your heating system, you need to try a flame sensor cleansing.

🔥 Steps to Eradicating the Carbon Buildup on Your Soiled Flame Sensor

furnace burners

5 Steps to Eradicating the Carbon Buildup on Your Soiled Flame Sensor

1. Safely Shut Off the Energy to the Furnace

To soundly shut off the facility to your fuel furnace, you need to first find the toggle swap or circuit breaker that controls the facility to the furnace.

That is sometimes positioned close to the furnace or in a central electrical panel.

If it’s close to your furnace, it would seem like a typical mild swap.

Upon getting positioned the swap or circuit breaker, you possibly can flip it off to close off the facility to the furnace.

Most furnace shut-off switches are positioned close to the furnace and seem like mild switches or toggle switches.

The precise location could differ between being mounted on the furnace itself, ceiling, or wall.

If the putting in contractor was a keener, then it could be labeled or have a pink cowl plate.

For those who can’t discover the shut-off swap, then you definately’ll should go to {the electrical} panel and search for the furnace breaker.

You may’t at all times belief the labeling on a swap or the breaker panel, so verify that the facility is off with {an electrical} multi-meter earlier than engaged on the furnace.

2. Take away the Flame Sensor

To take away a furnace flame sensor, you’ll first must find the sensor, which is often hooked up to the furnace close to the burners.

Upon getting positioned the sensor, you should utilize the 1/4″ or 5/16″ hex head nut driver to loosen the retaining nut or screw that holds the sensor in place.

As soon as the retaining nut or screw is eliminated, you possibly can rigorously slide the sensor out of its mount and take away it from the furnace.

You should definitely keep away from damaging the sensor or the furnace whereas eradicating it.

3. Easy methods to Clear a Soiled Furnace Flame Sensor

To wash a flame sensor, you’ll need to rigorously take away it from the furnace as described above.

Upon getting eliminated the flame sensor, you possibly can clear the metallic rod (not the ceramic tube) utilizing the emery material or a mushy material/brush and a few rubbing alcohol or electrical contact cleaner.

Gently scrub the sensor to take away any dust or particles, after which use a clear material to dry it off.

You should definitely keep away from utilizing any harsh cleansing brokers or abrasive supplies, as these can harm the sensor.

As soon as the sensor is clear, you possibly can reattach it to the furnace and take a look at it to make sure that it’s functioning correctly.

Do not forget that you’re solely trying to take away the particles and carbon buildup from the metallic rod and never attempting to make it shine prefer it was new.

For those who over-clean it, you might make it worse.

4. Easy methods to Re-install Flame Sensors

To re-install a flame sensor, you’ll need to rigorously slide the sensor again into its mount on the furnace.

As soon as the sensor is in place, you should utilize a hex head nut driver to tighten the retaining nut or screw that holds the sensor in place.

You should definitely tighten the nut or screw securely, however keep away from overtightening it, as this could harm the sensor or the furnace.

As soon as the sensor is securely hooked up, you possibly can re-attach {the electrical} wire and take a look at it to make sure it’s functioning correctly.

PRO TIP: it’s at all times a good suggestion to examine the resistance of {the electrical} wire going from the furnace flame sensor to the circuit board to verify that the wire isn’t damaged.

5. Easy methods to Be certain that the Furnace Flame Sensor is Working

To make sure your soiled sensor is functioning correctly, you possibly can carry out a easy take a look at by turning on the furnace and observing the burners.

The flame sensor ought to activate the burners and keep a gradual flame.

If the burners don’t ignite or the flame is just not regular, this will point out an issue with the flame sensor or one other element of the furnace.

On this case, you could want knowledgeable to examine and restore the furnace.

Moreover, you should utilize a multimeter to check the sensor for continuity, which may also help verify that it’s functioning correctly.


  • 1/4″ or 5/16″ hex head nut driver with a 6-12″ extension
  • A bit of emery material, or mild to medium grit sandpaper
  • Electrical contact cleaner

Supplies: A bit of emery material, or mild grit sandpaper, and paper towel or a clear rag

🔥 Easy methods to Substitute a Damaged Flame Sensor

glowing hot surface ignitor

In case your furnace flame sensor is just not working correctly, you’ll need to exchange it.

To do that, you’ll first must shut off the facility to the furnace to make sure that it’s secure to work on.

As soon as the facility is off, you possibly can comply with the steps for flame sensor substitute as described above.

As soon as the previous damaged sensor is eliminated, you possibly can set up the sensor as a replacement by rigorously sliding it into the mount and tightening the retaining nut or screw.

You should definitely use a brand new sensor that’s appropriate together with your furnace, and comply with the producer’s directions for set up.

As soon as the sensor is put in, you possibly can flip the facility again on and take a look at the furnace to make sure that it’s working correctly.

In case you are not sure easy methods to exchange the flame sensor or for those who encounter any difficulties, it’s best to seek the advice of knowledgeable HVAC technician for help.

🔥 The place to Purchase Furnace Flame Sensors for Your Furnace Model and Mannequin

cold woman shopping for furnace parts

The simplest means to purchase the right flame sensor is to contact the producer or a neighborhood provide home for the furnace model you’ve.

You’ll want the mannequin and serial quantity in your furnace in order that they’ll match the precise sensor rod.

For those who’re a gambler, then you might attempt to discover a common flame sensor on Amazon that features your furnace model and mannequin.

You’ll possible have the ability to make a common flame sensor work, but it surely’s at all times your finest wager to get the producer’s half if doable.

One of many common flame sensors that I wish to maintain in my service truck is the White Rodgers Common Flame Sensor.

If in case you have hassle contacting the producer, then your finest wager is to name a neighborhood contractor to get their assist.

You’ll must pay them, however your heating system shall be up and working a lot faster.

🔥 What’s Subsequent

Phyxter Approved Logo on Service Truck

As at all times, we like to tell our readers about different articles that might assist them with their furnace restore points.

So, if flame sensor substitute or cleansing didn’t get your burner meeting fired up then you need to learn our article on DIY Furnace Restore Issues and Options.

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