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Olive Explains the Faulty Flame Sensor in a Furnace

Flame Sensor

What do you want most from your gas furnace this winter? Warmth! But what happens if you’ve got a furnace that keeps shutting down each time you set your thermostat for it to turn on. Not much warmth, and that’s not much fun.

Gas furnaces that keep shutting down are a common furnace repair in Seymour, TN that our Russell & Abbott team handle. If you’ve got this problem, call us and we’ll find out what’s going on and take care of it.

But many of you would like to know the why of this situation—it’s the reason you come to read my blog. And I love to talk about how HVAC systems work because that’s what being an expert heating-and-cooling blogger dog is all about. So today let me tell you about a common reason for a gas furnace that won’t stay on: a faulty flame sensor.

What’s a flame sensor, Olive?

The name will give you a basic idea of what’s going on here. But what’s important to know is why a furnace has a flame sensor at all. A flame sensor is a component that detects when gas burners have ignited into the flames used to provide heat. If a flame sensor doesn’t detect that there are flames when the gas valve is open and sending gas to the burners, it shuts off the gas valve. This is a key safety feature that stops the flow of unburned gas into a furnace. 

Modern flame sensors replaced an older part that did a similar job, the thermocouple. Flame sensors are more accurate and reliable, so you can be confident the flame sensor in your furnace will do its job and keep your family safe.

But they can malfunction … let’s move on to that.

When flame sensors go bad

Any part of a furnace can wear down over time or get dirty, and a flame sensor is no exception. One of the reasons a flame sensor can start to lose its sensitivity to heat is because of carbon build-up, which is similar to the carbon build-up that can make the gas burners irregular. But plain ol’ dust can affect a flame sensor as well, which is yet another reason I stress with my readers to change the furnace filter regularly, which helps keep dust from inside the furnace. 

What to do about a bad flame sensor

An important reminder: if you suspect a faulty flame sensor is the reason your gas furnace keeps shutting down, please don’t open the furnace and try to repair it yourself! I want you to stay safe, as does everyone here at Russell & Abbott, so leave all repair work to our professionals. The flame sensor may not be the problem, and it takes experts to properly diagnose the issue.

If you do find a faulty flame sensor is behind your gas furnace woes, we can clean the sensor or replace it if it’s worn down too much. These are straightforward jobs that can help get your furnace back to working safely and reliably. We will never leave you with a furnace that might be unsafe!

One final friendly reminder: regular professional heating maintenance will help catch flame sensor problems early. Be sure to join our Comfort Club and we’ll fend off troubles before they happen!

Stay warm and safe,