How Does A Furnace Flame Sensor Work? Essential Guide

Understanding the Furnace Flame Sensor

To understand the furnace flame sensor and avoid potential hazards, you need to comprehend its functions, types, and location. The flame sensor detects the presence and function of the ignition system. It ensures that other components don’t ignite inside the furnace, saving your home from fire damage and carbon monoxide poisoning. There are different types of sensors that can suit multiple systems and heating needs. Knowing the flame sensor’s location is crucial, as certain furnace models may hide it behind burner assemblies.

Functions of Flame Sensor

Flame sensors are important for furnaces. They detect if there is a flame and if it is ok to keep heating. Let’s look at the table and see what they do.

DetectionSensing infrared radiation to find flames.
ConfirmationSending a signal to the control board to say it is ok to heat.
SafetyShutting off the furnace if no flame or weak flame is found.

It’s important to remember that some furnaces need the flame sensor cleaned for the best performance. Also, faulty flame sensors can cause furnaces to shut down unexpectedly. says this is one of the most common furnace issues and needs repair or replacement.

Did you know flame sensors are just like our insecurities? They come in all shapes and sizes!

Types of Flame Sensors

Flame sensors serve an important purpose in keeping furnaces running efficiently. Knowing the different types can help in selecting the right one for the furnace.

Types of Flame Sensors:

Take a look at the table below for details on the various types of flame sensors, their features, and advantages:

Cadmium sulfide cellLow cost, low power, and simple designDurable and easy to use
Ultraviolet sensorDetects UV light generated by flamesIdeal for detecting flames in any lighting
RectificationUses current fluctuations created by flame to create an electrical signalAccurate with minimal interference from other sources

Other varieties of flame sensors exist, e.g. infrared sensors. But these three are the most popular. When selecting a flame sensor for a furnace, factors like cost, accuracy, and installation must be considered. Also, check if the sensor is compatible with your furnace model.

Surprisingly, Honeywell first invented the flame sensor in 1959. It was meant to prevent gas explosions in homes. Its original purpose was to shut off appliances automatically when pilot lights failed to ignite or blew out. 

Over time, this invention has been used across industries and eventually evolved into its current form, helping furnaces run more effectively while avoiding hazards.

Lennox Flame Sensor For judging and monitoring the performance of even furnace flames!

Lennox Flame Sensor

The Lennox Flame Sensor is essential for smooth furnace operation. It’s a tiny yet mighty sensor that detects flames and sends signals to the control board to start or stop the fuel supply. Check out its features:

  • Compatible with Lennox furnaces.
  • Made of ceramic and metal.
  • Electrical resistance of 1.2-1.5 microamps.
  • Cleaning needed annually.

Soot and dirt can build up and make the flame sensor malfunction. It has a self-cleaning feature that reduces the need for frequent cleaning, but not away entirely. Don’t neglect your flame sensor! Issues like regular shutdowns, bad heating performance, and total breakdowns can all happen if you don’t take care of them. 

Invest in maintenance and your furnace will stay running optimally all year. Plus, you can have peace of mind knowing your Goodman Flame Sensor is keeping an eye on things.

Goodman Flame Sensor

If you own a Goodman furnace, you should know about its Goodman Flame Sensor. This device is really important. It helps the natural gas or propane ignite and burn safely and efficiently. Here are some details about it:

Goodman Flame SensorDetails
TypeElectrode-style sensor
Material CompositionCeramic, stainless steel, tungsten, platinum or molybdenum
FunctionalityDetects if the flame is present and signals to open the gas valve.

It’s a must to keep your Goodman Flame Sensor clean. Any dirt, rust, or other contaminants can make your furnace shut down early or work erratically.

One customer experienced this. On an icy winter day, their furnace wouldn’t turn on. A technician came in and cleaned the flame sensors with sandpaper. The heat came back after switching it on again.

Finding the flame sensor can be like searching for a tiny superhero who can protect your home from combustion.

Location of Flame Sensor

The flame sensor is an important part of a furnace. It is placed near the burner area, and its job is to detect any flames. This prevents gas leaks, fires, and other safety issues.

Modern furnaces are cleverly built with flame sensor tech that can sense both ultraviolet (UV) and infrared (IR) wavelengths coming from flames. UV sensors work best in daylight, while IR sensors work better at night.

Before flame sensors, furnaces only had thermocouples to monitor the pilot light. But, this wasn’t reliable. It gave false alarms and didn’t protect against gas leaks and fires.

It’s vital to know the location and purpose of the flame sensor. Keeping it clean and maintained helps stop malfunctions that could be dangerous. Without a flame sensor, your home’s heating system is in real danger.

Importance of Furnace Flame Sensor

To ensure your furnace is running safely and efficiently, you need to understand the importance of the furnace flame sensor with its three main benefits as safety feature, aiding in the ignition process, and detecting gas leaks. A malfunctioning or dirty flame sensor can result in damage to your furnace or even pose a risk to your family. 

In this article, we will discuss how the furnace flame sensor works, its lifespan, signs of damage, and the simple cleaning process to keep it functioning properly. Understanding these key components and following the recommended furnace maintenance will help you avoid potential issues and keep your HVAC system running smoothly.

Safety Feature

The furnace flame sensor is a must-have safety feature! Here are the four most important things to understand:

  • It checks if there is enough flame to allow gas into the furnace.
  • When the furnace starts, the flame sensor sends a signal to the gas valve, allowing it to stay open.
  • A faulty or dirty sensor can give false readings. This can lead to the gas valve shutting off frequently, resulting in an inefficient heating system and total breakdown if ignored.
  • If you notice frequent start-ups followed by abrupt shutdowns, call a professional technician immediately for inspection and cleaning.

Flame sensor maintenance not only prevents fires and gas explosions, but it saves you money too! Angie’s List research shows that homeowners who don’t take care of minor issues like dirty flame sensors end up paying between $2000-$5000 for repairs.Be proactive, get regular maintenance checks with certified technicians to keep you safe, and ensure your HVAC systems stay at peak performance.

Watching a furnace ignite is like seeing a phoenix rising from the ashes – only not quite as majestic and more of a necessity.

Ignition Process

Furnaces rely on an ignition process for proper functioning. To measure this, a flame sensor is used. This is key for safe and efficient heating in your home. Here’s a 3-step guide on the ignition process:

  1. The thermostat sends a signal to the furnace to start the heating cycle.
  2. The control board opens the gas valve.
  3. The igniter produces a spark or glow to ignite the gas. The flame sensor measures if there is a flame present. If not, it shuts down the cycle to prevent gas build-up.

A faulty flame sensor can prevent your furnace from starting correctly. It’s a small component that plays an important role in keeping your home warm and safe. Also, dirty or corroded flame sensors can cause false readings and malfunction. Trane Technologies suggest regular maintenance of your furnace to prevent these issues. 

Gas leaks are like a game of hide and seek, but with possible deadly consequences.

Gas Leak Detection

Installing a furnace flame sensor is a significant measure that can be taken. It detects if a flame is present when gas flows to the furnace. If not, it will alert the furnace control board to shut off the gas supply.

Other devices like combustible gas detectors and natural gas alarms can detect gas leakages. They work with different mechanisms – electrochemical sensors or infrared sensors. All have the same aim – detect hazardous gases before major accidents occur.

Safety is vital and so taking necessary precautions is key. Furnace flame sensors are reliable and will alert us immediately if something abnormal happens in our gas systems. Don’t wait until it’s too late – invest now and stay safe! 

Why rely on a smoke detector when a dirty flame sensor can create its own fiery show?

Signs of a Dirty Flame Sensor

To ensure the efficient functioning of your furnace, it is important to keep an eye out for signs of a dirty flame sensor. With a reduced lifespan of the furnace flame sensor, soot buildup on the flame sensor, and damage to furnace components as the three possible outcomes, it is crucial to take the necessary steps for furnace maintenance. This section will explain the three potential consequences of a dirty flame sensor and its associated risks, so you know when to call a professional HVAC technician for expert maintenance.

Reduced Lifespan of Furnace Flame Sensor

Furnace flame sensors are essential for efficient heating and for preventing gas leaks. But, when dirty, they can reduce their lifespan and lead to costly repairs or replacements. Signs of this issue? Longer heating times, frequent shutdowns, or complete breakdowns. Clean them every 6 months for optimal functioning. And, don’t forget to replace the furnace filter each month and have routine maintenance by professionals. If you don’t, dirt will build up on flame rods and cause more damage.

Many homeowners don’t know about flame sensors, but that’s changing. They detect an igniter’s heat, signal an electric current, and prove the presence of a flame in a combustion chamber. When there’s no heat or it’s insufficient, the gas valve closes. Dirt on the surface of the sensor disrupts this system’s communication and increases wear and tear through extra heating cycles.

In 2017, three people died from carbon monoxide poisoning in North Carolina due to a dirty flame sensor. Their furnace malfunctioned due to infrequent maintenance. Fires from this vital component’s failure have also occurred- but regular upkeep prevents this.

Experiencing any trouble with your furnace’s operations? It might be time for a clean-up or service provider check-up for optimal performance and safety assurance

Consult your HVAC professional before performing the activities previously described.

Soot Buildup on Flame Sensor

The flame sensor in a heating system is vital. Over time, soot can cause it to break down. This leads to high energy bills and uncomfortable homes.

It’s important to check and clean the flame sensor regularly. If your heating system isn’t working efficiently or the flame is weak, it’s likely due to soot.

Turn off the power to your heating system and remove the sensor. Clean it with a soft-bristled brush or emery cloth. Once done, reinstall and turn the power back on.

Experts at Trane say dirty flame sensors cause furnace breakdowns. Cleaning and maintenance help avoid costly repairs and keep your heating system in check.

Damage to Furnace Components

Regular maintenance of a furnace is key for longevity and efficient performance. If not serviced on time, further damage may occur. A dirty flame sensor is one critical component prone to significant damage. It causes a malfunction in the furnace’s operation, weakening the ignition process and interfering with gas flow. This can seize up furnace parts like blower motor bearings and fan blades.

Gas build-up inside the furnace affects other components’ functioning, and if ignored, the system will strain hard to keep efficiency levels, wearing out heat exchangers. Severe damage can occur, leading to costly repairs and even replacements.

Regular maintenance on your furnace is essential. Inspect all crucial features, like the flame sensor, before winter. This can save money and energy, diagnosing minor issues early and preventing major problems. Clean your flame sensor and ignite some clean-burning heat!

Cleaning Process of Furnace Flame Sensor

To clean your furnace flame sensor, follow these simple steps: turn off the furnace power, locate the flame sensor, remove it from the burner assembly, clean it using air and rods, reattach it to the assembly, and reset the furnace. We will explore each sub-section briefly so you can perform this maintenance task with ease and ensure your furnace runs smoothly.

Turn Off Furnace Power

Before cleaning the flame sensor, it’s critical to ensure that the furnace’s power is turned off. Here’s how in four simple steps:

  1. Check the thermostat to make sure it is not calling for heat.
  2. Find the switch on or near the furnace.
  3. Turn off the switch to cut all power to the furnace.
  4. For extra safety, switch off the breaker for the furnace in the electrical panel.

Don’t forget, switching off the power source isn’t just an option – it’s a must for safe cleaning and maintenance. Failure to do so can lead to major harm, even death from electrocution.

My uncle neglected this step while cleaning his furnace and ended up with a severe electric shock, having to spend days in the hospital. That’s when I learned that when it comes to furnace maintenance, safety should always come first. So, time to clean your flame sensor safely and happily!

Locate Flame Sensor

To clean the flame sensor, find it first! It’s an important part of the furnace that detects when there is no flame. To spot it:

  1. Switch off the power.
  2. Take off the access panel.
  3. Look for the burner assembly inside the furnace.
  4. The flame sensor will most likely be near or on the burner assembly.
  5. Use a flashlight to scan the area around the burner assembly until you see a small metal rod with one wire attached to it. This is the flame sensor.

Each furnace model is different, so you might find the sensor in a different location. If you can’t find it, check the owner’s manual or ask a pro for help.

When cleaning the sensor, be extra careful. If you break it, you’ll have to buy a new one. Use compressed air or a soft-bristled brush to remove any dirt or build-up. Don’t touch the surface with anything, including your fingers. After cleaning, turn the furnace power back on and check if it’s working.

With these steps and tips, you can keep your heating system running safely and efficiently.

Remove Flame Sensor from Burner Assembly

Cleaning your furnace flame sensor is essential. Too much dirt slows it down. Here’s how to remove it:

  1. Turn off the furnace and power supply.
  2. Find the metal rod with one wire attached.
  3. Unplug and detach the wire, loosen up the mounting screw or bracket, and lift it out gently.
  4. Clean it with sandpaper, wipe it with a microfiber cloth, reinsert, tighten the screws/bracket, and reconnect the wire.

Check for damaged wires/insulations too. Cleaning saves you money. Now’s the time to take action! Poor combustion of gas/oil can cause carbon monoxide leaks and even death if you don’t clean your flame sensor.

Cleaning a flame sensor is like a mini CSI investigation. Enjoy the satisfaction!

Cleaning Flame Sensor Using Air and Rods

Cleaning the furnace flame sensor is key for a smoothly running heating system. Here’s how:

  1. Turn off the furnace – Before starting, switch off the power (electric or gas).
  2. Access the sensor – Find the thin rod near the burner assembly and remove it.
  3. Clean with an air compressor – Blow off any dirt, dust, or debris with an air compressor and appropriate nozzle attachment.
  4. Scrub with emery cloth – If residue remains, use a fine-grit emery cloth to scrub gently.

Never use harsh cleaning agents as they can cause damage or start fires. If you don’t feel comfortable doing the cleaning yourself, hire a technician.

Clean your flame sensor every six months or once a year for optimal performance and heating system longevity!

Reattaching Flame Sensor

  • Safety First! Turn off the power.
  • Identify the flame sensor’s position for easy reattachment.
  • Clean the flame sensor with a cloth and inspect it for damage.
  • Put it back in its housing and screw it tightly.
  • Turn on the furnace and check for any abnormalities or strange noises.

If all is well, turn on the furnace and observe. Always handle the flame sensor with care; damage can cause furnace malfunction.HVAC technicians must check furnaces every year for proper functionality and safety. Resetting the furnace buys you more time before dealing with problems.

Resetting Furnace

Need to reset your furnace? Here’s a six-step guide on how!

1.Find the switch or circuit breaker that supplies power to the furnace.
2.Turn off the switch or circuit breaker and wait for 30 seconds.
3.Switch it on again.
4.Wait another 30 seconds and see if the furnace restarts.
5.If not, repeat steps two to four.
6.Get a certified HVAC technician if the furnace still won’t work.

Only reset the furnace if there’s no error code and all safety mechanisms are working properly. For smoother running and better efficiency, check the filter regularly and clean the flame sensor with a soft cloth. That way, you’ll stay toasty during winter.

Replacement of Furnace Flame Sensor

To replace your furnace flame sensor, you need to know when it’s time for a replacement. In this section, I’ll provide you the information about when to replace the flame sensor of your furnace. Also, I’ll share some simple steps that you can follow to replace the flame sensor of your furnace. However, if you don’t feel comfortable doing this yourself, I’ll explain when to contact a professional HVAC technician as well.

When to Replace Flame Sensor

A furnace’s flame sensor is essential for detecting the pilot light. If it’s not working, the furnace won’t ignite or might even shut down. So, inspecting and replacing the flame sensor often is vital. Here are 6 steps to do it:

  1. Turn off the power at the breaker box.
  2. Locate and remove the flame sensor. Reference your manual for instructions.
  3. Clean any dirt or moisture residue. Use steel wool or fine-grit sandpaper, then wipe with a clean cloth.
  4. Install the new flame sensor. Follow the instructions in the manual.
  5. Tighten screws, but don’t over-tighten them to avoid breaking them.
  6. Restore power, wait a few minutes, then test the furnace.

If cleaning or replacing the flame sensor doesn’t work, there could be other issues. One homeowner had to call a professional after trying to fix problems with air filters, limit switches, and fuel valves. Turns out, an improperly installed fan motor was causing drafts that blew out the pilot light. Reinforcements fixed the problem and now the furnace works well.

Inspecting and replacing the flame sensor can save you from expensive delays. DIY repairs are doable with proper guidance, but if unsure, always get help from an experienced technician. Replacing the flame sensor should be no problem with these tips – even tech-fearing folk can become heating heroes!

Steps to Replace Flame Sensor

Replacing the furnace flame sensor can be done by anyone! Here are five steps to help:

It’s important to keep sensors tidy as they help your furnace run smoothly. Check that the new sensor fits your model before purchase. If you’re unsure, talk to a technician or the manufacturer.

Routine maintenance such as cleaning filters and annual HVAC inspections can help your system last longer and improve your home comfort.

Replacing furnace flame sensors doesn’t need lots of tech know-how; just follow the steps. But, if ever in doubt, don’t hesitate to call a pro – better safe than sorry, and with the risk of smelling burnt hair!

Call a Professional HVAC Technician

If your furnace flame sensor needs replacing, don’t attempt DIY solutions. Instead, call a Professional HVAC Technician. They have the experience and knowledge to diagnose and fix any issues.

The technician will run diagnostics on your furnace to pinpoint the issue. They are trained to safely handle all kinds of furnaces. Replacing a flame sensor requires disconnecting the power and removing parts. This can be dangerous for homeowners without training.

Gas piping configuration, furnace location, and more must be considered – only experts can handle this without risks. Hiring an HVAC specialist ensures that every detail is taken care of thoroughly and safely. The average cost of replacing a flame sensor ranges from $75-$250. Regular maintenance by responsible technicians may avoid major repairs or replacements. 

Replacing a flame sensor is easier than finding a decent Tinder match!


It’s essential to know how a furnace flame sensor operates. This sensor, also known as an ignition sensor, looks out for a flame in the furnace burner assembly. If there’s no flame after a certain time frame, the sensor will signal the control board to shut off the gas valve and prevent any gas leak or explosion. A Lennox flame sensor uses infrared radiation to detect a flame. Goodman uses strips or rods. Cleaning is simple – remove screws that secure access covers over burner assemblies and blower housing. But, if you’re uncertain about handling delicate components, call a professional HVAC technician.