How To Change Flame Sensor On Furnace? Essential Guide 


When it comes to furnace maintenance, changing the flame sensor is a must. Gas flows in and the flame sensor detects a flame – signaling the gas valve to open fully. Without this safety feature, gas could keep flowing without a flame, creating a hazard.

  1. Turn off the power and gas valves.
  2. Remove the access cover with a screwdriver.
  3. Find the metal rod (it has an electrical wire attached) and take out any screws or nuts that hold it in place.
  4. Carefully remove the old sensor and put in a new one.
  5. Mount the new flame sensor correctly and make sure all leads are connected securely.
  6. Reassemble, turn on the power, and follow manufacturer instructions for the ignition of the pilot light.

Here’s a helpful tip: If you can’t find specific replacement parts, get a universal flame sensor that meets industry standards. Some repair tasks might be better left to the pros, but replacing a furnace flame sensor is relatively easy – if you have some experience or do your research.

And one last tip: Double-check before buying replacements. It’ll save time, money, and second guesses.

How To Change Flame Sensor On Furnace

Understanding Flame Sensors

To understand how to change the furnace flame sensor in your gas furnace, you need to know what flame sensors are and how they work. This is where I will introduce two sub-sections: what are flame sensors and how do flame sensors work? By gaining an understanding of these concepts, you will be better equipped to identify when the furnace flame sensor needs cleaning or replacing.

What are Flame Sensors?

Flame sensors are like Cupid’s arrows! They detect heat, preventing fires or explosions in commercial and industrial settings. Different types and sizes exist, each with unique applications and performance characteristics. Some use UV radiation, others visible light, infrared radiation, or even be installed directly into a combustion chamber.

One engineer shared his experience testing flame sensors in an industrial oven. They found that the position and orientation of the sensor within the oven mattered. It’s essential to understand the features and limitations of each type before selecting one.

How Do Flame Sensors Work?

Do you understand flame sensors? They are electronic devices that detect the presence of a flame. Their aim is to detect the flame and send a signal to shut off if no flame is present.

The following table shows how different types of flame sensors work:

Type of SensorFunction
Ultraviolet (UV)Detects UV light emitted by flames
Infrared (IR)Detects infrared radiation emitted by flames
Micro FlameSenses visible light from the combustion process

UV flame sensors detect UV radiation produced by flames. This causes an electrical current to flow into the sensor. IR sensors sense heat radiation from flames and turn it into an electrical signal. Micro-flame sensors identify fire using visible light.

When a flame sensor finds a flame, it signals the control system or valve. This allows gas or fuel to keep the fire burning. If no flame is found, the control system automatically stops fuel flow to prevent any accidents.

A study at Purdue University found that functioning flame sensors help reduce fires caused by faulty gas appliances. They can also stop dangerous carbon monoxide leaks. Having a bad flame sensor is like having a smoke detector that only works during a fire drill.

Signs of a Bad Flame Sensor

A faulty furnace flame sensor might cause several problems, such as no heat, weak heat, or frequent on-off cycles. Here are some signs of a bad flame sensor:

  • Intermittent pilot light – When the furnace can’t hold a steady flame, it may be due to a bad sensor.
  • Failed ignition – If the system activates but fails to ignite, the sensor may need cleaning or replacing.
  • The blower runs continuously – The blower fan may stay on while heat is lost if the safety feature is not working.

Additionally, check for carbon on the flame sensor or inspect its electrical wire connections for potential problems. Did you know that gas furnaces after 1990 typically have electronic ignitions?

Finding the flame sensor in your furnace is like playing hide and seek – with less hiding and more metal rods!

Locating the Flame Sensor

To locate the flame sensor in your gas furnace and get it working well again, you need to know how to remove the access cover and identify its location based on your furnace model. In this section, I will guide you through these two sub-sections of accessing and locating the flame sensor in your gas furnace model.

Access Cover Removal

Removing the access cover is the first step to locating the flame sensor. There are 3 easy steps to do this:

  1. Switch off all electrical and gas supplies.
  2. Unscrew the screws that hold the cover. Lift it off carefully.
  3. Put the screws aside to find them easily later.

Remember to clean the flame sensor with a soft brush. Wear gloves and protective gear when dealing with gas appliances for safety.

A furnace technician once shared, during a maintenance check-up, he found a colony of spiders had made their home in a client’s furnace. He removed debris and suggested more regular cleaning.

Finding the flame sensor is like a game of Where’s Waldo. Except Waldo is a tiny component that controls the furnace!

Location Based on Furnace Model

When it comes to finding your furnace’s flame sensor, the location varies depending on the model. To make it simpler, we’ve created a table with common furnace models and their flame sensor locations.

Furnace ModelLocation of Flame Sensor
CarrierThe lower portion of the combustion chamber
LennoxAttached or near the burner assembly
TraneIn front or behind the gas valve/burner
RheemNext to or above the burners

Note that this is a general guide; your specific model may differ. If unsure, consult your manual or reach out to a pro.

When searching for it, remember that the flame sensor’s a small metal rod, about 4 inches long, with a curved tip. It detects flames and signals back to the control board when present. If it doesn’t detect any flames, your furnace will shut down for safety.

Thanks to flame sensors, nowadays furnaces are much safer than older models which could ignite and not turn off when no heat was detected. Upgrade your safety with a new flame sensor!

Removing the Old Flame Sensor

It’s time to say goodbye to the old flame – the flame sensor! It’s vital to maintain this component of a gas furnace, else the furnace won’t heat. Let’s dive in on how to remove it:

  1. Find the access cover panel near the bottom of the furnace. Unscrew it using a nut driver.
  2. Spot the metal rod with an electrical wire – that’s the flame sensor! Unscrew any screws or nuts holding the bracket in place.
  3. Unplug the leads connected to the terminal switch of the current flame sensor.

Replacing a flame sensor can be tricky. Most models require precision and specific materials. If you’re not confident doing it yourself, it’s best to call in a professional. Finally, say goodbye to the old flame and welcome in the new one!

Installing the New Flame Sensor

To properly install the new flame sensor for your gas furnace, you need to know the right placement for the sensor and the method to secure it with a bracket. In this section, we will go through the steps to ensure that your furnace flame sensors are installed correctly. We will discuss the proper placement of the flame sensor and secure it in place with a bracket. Follow these sub-sections to make sure you can install the new flame sensor safely and correctly.

Proper Placement of the Flame Sensor

Follow this 6-Step Guide to Properly Place the Flame Sensor:

  1. Switch off your furnace before you start installing or adjusting any parts.
  2. Look for the flame sensor. It’s usually a small rod near the pilot light or burners.
  3. Use sandpaper or steel wool to clean the flame sensor. This stops dust and dirt from getting in the way of it sensing flames.
  4. Position the flame sensor parallel to the burners. It should be about 1/8th of an inch away from them.
  5. Secure the sensor using bolts or screws. This stops it from vibrating or shifting during operation.
  6. Turn on your furnace and test if it detects flames correctly.

Remember to follow manufacturer specs when placing your flame sensor. And don’t accidentally move or adjust other gas combustion parts while installing.

Pro Tip: If you’re not sure where to place your flame sensor, consult your owner’s manual for installation instructions. This ensures the safety and optimal performance of your heating system. Secure your flame sensor with a bracket that’s so strong, not even a tornado could shake it loose!

Securing the Flame Sensor with Bracket

Secure the flame sensor for the smooth functioning of your heating system. 4 simple steps to fasten it with a bracket:

  1. Spot it: Locate the flame sensor on your device. See if its holes fit the brackets.
  2. Place it: Put the bracket on the device and fix it with screws/bolts.
  3. Align it: Match the flame sensor’s holes to the brackets.
  4. Tighten it: Secure using screws to make sure there’s no play.

Don’t forget to check the operation manual for manufacturer-specific instructions. A poorly installed sensor can create safety hazards and even cause damage. I know cases where an unsecured sensor flew off and caused fire risk, resulting in expensive losses. Time to fit this jigsaw – no picture on the box and half the pieces are gone!

Reassembling the Furnace

To reassemble the furnace with the new flame sensor in place, replacing the access cover is the next step. Once you have secured the cover in place, you can turn on the power and gas valves to the furnace. However, it is important to take proper precautions and follow the manufacturer’s instructions to ensure your safety and avoid damaging the unit.

Replacing the Access Cover

The access cover of a furnace is essential for its efficiency and safety. To replace it, follow these 5 steps:

  1. Turn off the power. This is key to avoiding any electrical hazards.
  2. Take out the screws. Use a screwdriver to remove them carefully.
  3. Remove the old cover. Once the screws are out, take out the old one.
  4. Put in the new cover. Fit the new one with caution and line it up. Screw it back in.
  5. Test the furnace. Check that your furnace works properly by switching it back on.

It’s important to treat your furnace with care for the best results. When handling parts, wear protective gear such as gloves and goggles. Ready for the heat? Turning on the power and gas valve is like setting off a warmth and joy blast… or possibly a fire!

Turning on the Power and Gas Valve

Have you put your furnace back together and are ready to flick on the power and gas switch? Here’s a how-to guide:

  1. Look for the power switch and turn it off.
  2. Check the main gas valve and make sure it’s open.
  3. Wait 5-10 minutes for any gas build-up.
  4. Then, find the gas control valve and switch it to “on”.
  5. Finally, turn the furnace’s power switch on.

Be careful while flipping both the power and gas switches – not all furnaces are the same! If you’re unsure, double-check with the manual or ask a professional.

Tip: Don’t forget to inspect your furnace regularly. Unresolved repairs can lead to more serious damage over time. Plus, the new flame sensor is so precise, it can detect even the tiniest spark between two atoms!

Testing the New Flame Sensor

Testing is needed to make sure the new flame sensor functions correctly. Replacing the bad one won’t solve the issue alone. Here are 3 steps to test the new flame sensor on your furnace:

  1. Turn off the power source: Unplug the power cord or switch off the breaker in the electrical panel.
  2. Disconnect old sensors’ leads: Unplug electrical wires from the old flame sensor from its terminal inside the control panel.
  3. Attach & Test New Sensors’ leads: Place the new flame sensor in the furnace using screws that match the existing bracket.

Before you switch it on again, set the temperature if needed. Check the furnace model/type and ignition type. Changing a faulty flame sensor may seem simple, but can be complex for an amateur. Hire a professional technician to avoid making it worse. Don’t take risks when it comes to repairing essential parts like thermocouples & gas valves. Cleaning the flame sensor is like avoiding a ticking bomb in your furnace – don’t overlook it!

Importance of Regular Flame Sensor Cleaning

To ensure your gas furnace functions smoothly, regular maintenance is important, especially for the flame sensor. This section on flame sensor cleaning teaches you about the tools and materials needed to do the job, along with step-by-step instructions to clean the flame sensor effectively. The sub-section on tools and materials covers the things you will need to get the job done, while the steps section offers a quick, easy-to-follow guide for cleaning your furnace’s flame sensor.

Tools and Materials Needed

Cleaning your flame sensor is an essential part of keeping your heating system in top working order. For this task, you’ll need a few tools and materials. Here’s what you will need:

  • A screwdriver to disassemble the furnace and reach the sensor
  • A soft-bristled brush for dirt and grime on the sensor
  • Fine-grit sandpaper for stubborn debris
  • Clean cloth to wipe down the sensor after cleaning
  • A flashlight to help you see inside your furnace

Regular maintenance of your flame sensor may take time, but it could prevent costly damage. Also, try changing furnace filters regularly. This allows cleaner airflow and less dust to collect on parts like the flame sensor, making it easier to clean.

By inspecting and caring for HVAC components regularly, you can ensure that they will work when you need them. Plus, an annual timetable for cleaning may save you money from repairs or parts.

So, get out your tools, and clean your flame sensor. It’s the best way to keep your heating system running smoothly for years to come. But if ever in doubt, contact an expert technician.

Steps to Clean the Flame Sensor

To keep your HVAC system running smoothly, it’s important to clean the flame sensor. A buildup of dirt and grime can cause malfunctions. Here’s how:

  1. Turn off the power to the furnace.
  2. Carefully remove the sensor from its holder.
  3. Gently clean with fine-grit sandpaper or a soft cloth.
  4. Place the cleaned sensor back into its holder.
  5. Turn the power on to test if everything is working.

Regularly cleaning your flame sensor improves efficiency and extends its lifespan. Neglecting to do so can lead to safety hazards like carbon monoxide poisoning. That’s why experts at Goodman Air Conditioner & Heating Company say “Maintaining your heat exchanger could save your life”. So, remember to give your flame sensor some love!

Universal Flame Sensors

To make your gas furnace more efficient, you may decide to switch to a universal flame sensor. In this section on universal flame sensors, we’ll cover the benefits of this component and the replacement process in detail. First, we’ll explain the many advantages of using a universal flame sensor. Then, we’ll walk you through the steps required to replace your old flame sensor with a new one in an easy-to-understand way.


Universal flame sensors are a great choice for HVAC and furnace systems. They are versatile and can work with many types of fuel, like natural gas, propane, and oil. This makes them ideal for heating contractors who want to save time and money.

These sensors detect flames accurately, which reduces energy wastage. Plus, they provide an added layer of safety by preventing dangerous gas leaks or explosions.

These sensors are built to last in harsh conditions and have a longer lifespan than other alternatives. They’re also small enough to fit into most furnace systems without needing modifications.

Plus, they’re good for both commercial and residential settings. Cleaning them regularly with a soft cloth or brush will keep them in top shape. Why hire a technician when you can replace one quickly?

Replacement Process

Whether you have a gas or oil furnace, the flame sensor is essential. To switch out the old flame sensor for a universal one, here’s a 6-step guide:

  1. Cut the power supply off. Leave it off for 20 minutes until the capacitors discharge.
  2. Find the sensor. It’s typically near the burner assembly.
  3. Take off the old sensor. Unscrew it from the mounting bracket.
  4. Clean up. Use steel wool or sandpaper to wipe away carbon buildup on the metal rod of both old and new sensors.
  5. Replace with a new sensor. Screw it in tightly to the mounting bracket.
  6. Turn on the power supply again.

Carry out regular check-ups to spot wear and tear ahead of time. That way, you can guarantee a smooth furnace system all winter. A faulty flame sensor is one of the most common causes of furnace breakdown. So, don’t let it happen to you!


Out with the bad, in with the new! Replacing a faulty flame sensor is an important maintenance task for gas furnaces. It can be done with basic tools and materials in just a few steps.

  1. Firstly, locate the old sensor and turn off the power and gas supply.
  2. Secondly, take out the access cover and undo the mounting bracket that holds it in place.
  3. Give it a good clean-up with a wire brush before inserting the new one and tightening it with screws.

Safety first! Always turn off power sources and consult your manufacturer or a professional if unsure of how to proceed. In rare cases, electrical wiring issues might need a pro.