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

🔥 Why Does Your Furnace Hold Shutting Off?

Probably the most widespread signs of furnace failure is brief biking.

In case you had 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 gasoline valve opens, the flame lights, the sensor detects the pilot flame (or doesn’t), after which the primary burners gentle.

If the whole lot above occurs besides the primary burner doesn’t gentle up, you almost certainly have a nasty 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 if 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 on the whole, are often made up of a skinny metallic rod operating 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 gasoline furnace management board.

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

When the gasoline 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 manner, if the Scorching Floor Ignitor or Spark Ignitor didn’t gentle the flame, you wouldn’t have gasoline buildup in your furnace as a result of the circuit board would routinely shut the gasoline valve.

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

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

🔥 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 go away 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.

As a rule, flame sensors are simply soiled and haven’t utterly failed.

So, earlier than you exit and purchase a brand new flame sensor to 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 ability to your gasoline furnace, you need to first find the toggle change or circuit breaker that controls the ability to the furnace.

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

If it’s close to your furnace, it would appear like an ordinary gentle change.

After getting situated the change or circuit breaker, you possibly can flip it off to close off the ability to the furnace.

Most furnace shut-off switches are situated close to the furnace and appear like gentle switches or toggle switches.

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

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

In case you can’t discover the shut-off change, then you definitely’ll need to go to {the electrical} panel and search for the furnace breaker.

You possibly can’t at all times belief the labeling on a change or the breaker panel, so verify that the ability 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.

After getting situated the sensor, you should use 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.

Make sure to 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 will have to rigorously take away it from the furnace as described above.

After getting eliminated the flame sensor, you possibly can clear the steel rod (not the ceramic tube) utilizing the emery fabric or a smooth fabric/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 fabric to dry it off.

Make sure to keep away from utilizing any harsh cleansing brokers or abrasive supplies, as these can injury 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.

Keep in mind that you’re solely making an attempt to take away the particles and carbon buildup from the steel rod and never attempting to make it shine prefer it was new.

In case you over-clean it, you might make it worse.

4. Easy methods to Re-install Flame Sensors

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

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

Make sure to tighten the nut or screw securely, however keep away from overtightening it, as this may injury 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 substantiate 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 preserve 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 part of the furnace.

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

Moreover, you should use 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 chunk of emery fabric, or gentle to medium grit sandpaper
  • Electrical contact cleaner

Supplies: A chunk of emery fabric, or gentle grit sandpaper, and paper towel or a clear rag

🔥 Easy methods to Change a Damaged Flame Sensor

glowing hot surface ignitor

In case your furnace flame sensor is just not working correctly, you will have to switch it.

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

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

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

Make sure to use a brand new sensor that’s suitable 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 ability again on and take a look at the furnace to make sure that it’s working correctly.

If you’re not sure how you can exchange the flame sensor or should you 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 approach to purchase the proper flame sensor is to contact the producer or a neighborhood provide home for the furnace model you’ve gotten.

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

In case you’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 be capable to make a common flame sensor work, however it’s at all times your finest guess to get the producer’s half if potential.

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 bother contacting the producer, then your finest guess is to name a neighborhood contractor to get their assist.

You’ll must pay them, however your heating system might be up and operating 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 would 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.