An Introduction To Furnace Flame Sensor Repair


HVAC equipment is complex, and homeowners can't be expected to understand every component inside their furnace and air conditioner. However, learning about your furnace flame sensor will help you keep your furnace running safely.

This introduction to furnace flame sensors will help you identify and fix a faulty flame sensor in your own furnace.

What is a Furnace Flame Sensor?

The flame sensor is a safety component on the burner assembly inside your furnace. The flame sensor looks like a thin metal rod and is usually positioned very close to the pilot light. The flame sensor monitors the pilot light flame and signals the gas line valve to close if the flame goes out.

The flame sensor keeps your home safe by preventing carbon monoxide buildup. A dangerous gas leak could occur if the gas valve didn't close when your pilot light went out. Flame sensors replaced thermocouples in newer furnaces with electronic pilot light controllers.

What are the Signs of a Bad Flame Sensor?

If your flame sensor is faulty, your furnace may exhibit a problem known as short cycling. Your furnace may run for a few seconds or minutes only to shut down again when the burners go out.

Short cycling occurs because the pilot light ignites, but the flame sensor doesn't detect that it's lit and shuts your furnace down as a safety precaution. If you open your furnace access panel and observe the flame sensor, see if the tip appears to be black with soot or if the porcelain pieces appear cracked.

What are Your Options for Flame Sensor Repair?

A cracked flame sensor must always be replaced. DIY-oriented homeowners can shut off the power to their furnace and remove the sensor on their own. In most furnaces, the sensor is simply mounted with a screw and connected by a single wire. Alternatively, you can hire an HVAC technician to confirm that the sensor is defective and replace it for you.

If your flame sensor doesn't appear cracked but is simply caked with soot, you may be able to clean the sensor to restore its function. Shut off the power to your furnace and use steel wool or fine-grit sandpaper to carefully scrub only the metal part of the sensor. Finish by wiping it down with a cloth or paper towel.

If you have trouble locating the flame sensor in your furnace, look for a model number on the side of your furnace and search for the owner's manual online. Use these tips or call an HVAC repair professional to fix your flame sensor if you are having problems with furnace short cycling.


14 October 2021

Shopping For A New HVAC System

After my sister moved into my house with me, she started complaining about the temperature. I had never really thought about it before, or maybe I was just used to it, but my house was pretty cold. She told me that she didn't think the furnace was working properly, so I started checking things out on my own. Sure enough, my furnace seemed to be having some serious problems. I started looking for a replacement, and I was able to find a great furnace for much less than what I initially thought I would need to spend. I wanted to make this blog for anyone out there who might need to shop for a new HVAC system. Check out these great articles for information you might need.