Cleaning a Dirty Flame Sensor

Waking up in the morning to a freezing cold house and a furnace that isn’t working isn’t a good feeling. The problem could be something complex and serious and you may need a local HVAC contractor to come out for emergency repairs. However, there is also a good chance that the problem is a dirty flame sensor. This small component is a crucial part of your overall system, your furnace will not run if the part is broken or dirty.

You may be wondering if cleaning a dirty flame sensor is a job that you can do yourself. While calling your technician for repairs is always a safe bet, some people may feel comfortable troubleshooting this problem on their own. Here is everything you need to know about your flame sensor, why it may not be working, and how to clean it. 

What Is a Flame Sensor? 

When your gas valve turns on and releases gas into the furnace, the ignitor should ignite the gas to create a flame in the system. Every furnace needs a way to protect the home in case the ignitor doesn’t work. A flame sensor is there to make sure the gas is ignited so that you are protected from gas explosions in your home. The flame sensor is a small rod that is able to detect whether or not there is a flame. If the gas doesn’t ignite, the flame sensor will know and will shut off your furnace so that no more gas is released. 

Is Your Flame Sensor Bad? 

Over time, your flame sensor can get a build-up of carbon from being exposed to flames over and over again. It can also get coated with dirt and dust that can end up in your furnace. You’ll know your flame sensor needs a repair or replacement if you see these signs: 

Burners Won’t Stay On

If you look inside your furnace and see that your furnace kicks on, but the burners only stay on for a few seconds before switching off again, it’s likely that you have a problem with a dirty flame sensor. You can see this by taking off the cover of your furnace, turning your furnace on, and looking to see if the burner stays on or not. 

Cracks on Your Flame Sensor

You can give your flame sensor a visual check to see if it’s in good condition. If the porcelain is cracked it can’t properly detect heat anymore and it will need to be replaced. If you have furnace problems, follow the steps below to look at your flame sensor, or call for repairs. 

There Is Build-Up on the Rod

While you’re looking at your flame sensor, check to see if the rod is blackened or if it has dust and other build-up on it. The rod should look clean and shiny. 

How to Clean Your Flame Sensor

If you are handy, you may be wondering if cleaning a flame sensor is something you can do yourself without having to call a professional. If you are feeling confident, you can follow a few steps to clean the sensor on your own. 

Step 1: Safety First!

When you’re doing any HVAC maintenance, you need to make sure to ensure your safety first. In the case of a dirty flame sensor, make sure to switch off the furnace. You may find a light switch next to the furnace that will turn off the power. Otherwise, to be safe, you can turn off all power to the system by flipping the breaker to “off.” In some systems, you may need to turn off the gas valve instead. Since this is a crucial step, if you feel unsure about it, you will want to get the help of a local HVAC contractor for repair services. 

Step 2: Locating the Sensor

You’ll be able to see where the flame sensor is by opening the cover to your furnace and looking for a single wire that is attached to the burner assembly with a screw. Sometimes the flame sensor is located on the opposite side of the assembly from the ignitor. At other times, it could be in a less accessible location. In this case, it may be easier to call for an HVAC repair. 

Step 3: Taking Out the Sensor

The next step of the process is taking out the dirty flame sensor. It’s usually only held in by one hex screw. Once you unscrew that, it’s easy to take the flame sensor out. The flame sensor itself may have a straight rod or a rod that’s shaped like an “L”. Make sure to not touch the rod of the flame sensor because you don’t want oil from your finger getting on it and attracting more dust. 

Step 4: Cleaning the Sensor

To clean the sensor, you’ll need some sort of material that is slightly abrasive but won’t scratch or damage the sensor. You don’t want to scratch the sensor because it will give the dirt and dust an even better surface to collect on and you’ll have the problem again more quickly. 

When choosing something to clean it with, think of the type of materials you might use to clean a non-stick pan. Something like a gentle scouring pad can work well. Very fine sandpaper cloth can be a good alternative. Some people use heavy-duty paper or even a crisp dollar bill to get the job done. 

Step 5: Putting the Sensor Back In

After the flame sensor is shiny again, all you have to do is put the flame sensor back in the hole, and replace the screw. Then you can test the furance to see if it is working again. If everything looks good, replace the furnace cover and enjoy your warm home!

Call SPH for HVAC Services!

Keeping your flame sensor clean is an important part of HVAC maintenance. During your annual furnace tune-up, you can advocate for your system and make sure your technician cleans the flame sensor as part of the tune-up. When you choose our HVAC services at Stith Plumbing and HVAC, you can always be sure that you will get comprehensive maintenance and repair services.  For furnace services in Springdale, AR or nearby areas, give us a call.