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know When To Replace A Furnace Flame Sensor | CroppMetcalfe

Nov 05, 2021

A CroppMetcalfe skilled professional standing next to a broken furnace flame sensor.


Your furnace’s flame sensor is a crucial aspect of maintaining the safe operation of the unit. The flame sensor’s main purpose is to prevent your furnace from triggering a gas leak or a consequential explosion. Understanding your furnace flame sensor is an important responsibility for any homeowner. 


Not only will you be knowledgeable about the purpose of the flame sensor, but you can recognize when it’s become faulty,  so you can get it replaced quickly and efficiently. Ignoring a flame sensor that needs to be replaced puts you, your home, and your family in danger. Read on to learn when to replace a furnace flame sensor and how to overall go about a furnace flame sensor replacement.

What is a Furnace Flame Sensor?

The furnace flame sensor is located inside the burner assembly area of your furnace. As its name implies, it carefully monitors whether or not a fire is lit inside the unit. If the sensor is not detecting an active flame, it will automatically turn off your furnace to prevent a dangerous gas leak from occurring.


The entire purpose of a furnace flame sensor is to prevent gas leaks and explosions. If there is no flame inside the furnace and leaking gas is allowed to continually flow throughout the home, carbon monoxide can build up and end up poisoning the residents of the home. An explosion is also possible. 

Signs a Furnace Flame Sensor Replacement is Needed

A quick troubleshooting inspection can help determine if your furnace flame sensor is working properly or not. Whether your furnace is making strange noises, releasing odd smells, or simply not operating correctly, always be incredibly careful during inspections.


To properly inspect your furnace flame sensor, turn off the power to your furnace and completely close the gas valve. Carefully remove the mounting screw and then remove the flame sensor. Inspect it gently, checking if the insulation appears intact or not. If your flame sensor only appears dirty, a good cleaning could fix the issue. If it appears broken or damaged, it likely needs replacing.


Here are some signs that your furnace flame sensor is bad:


  • The flame sensor appears corroded or sooty
  • The furnace will light but it shuts down after a few seconds and only operates in short cycles
  • The flame sensor porcelain is broken or cracked

A flame sensor that’s gone bad will not be able to sense the heat or flame of the furnace and end up shutting it down unnecessarily. This is the easiest way to know when to replace furnace flame sensors.

How to Handle a Furnace Flame Sensor Replacement

Cleaning the furnace flame sensor could be all that’s needed to get your furnace up and working again. However, if the furnace flame sensor is broken, cracked, or if there are any pieces missing, then it likely needs replacing. The best method for handling a furnace flame sensor replacement is to call in professionals. Dealing with furnace repairs can be tricky and sensitive. Save yourself time, stress, and mistakes by trusting the skilled professionals at CroppMetcalfe with the job.



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