Your guide to troubleshooting furnace flame sensor issues

Buddy's Air Conditioning & HeatingUncategorized

If your home has a gas furnace, your furnace has a furnace flame sensor. But, just what is this component, and why is it so important? Further, why do furnace sensor issues lead to a furnace breakdown? In this article, we’ll review everything you need to know about flame sensors, what can go wrong with them, and when you should call our team at Buddy's Air Conditioning & Heating for 24/7 emergency heating repair.

If your flame sensor shuts down the gas valve to your furnace, it's either because it no longer detects ignition—such as that seen above—or because of a fault with the sensor.
If your flame sensor shuts down the gas valve to your furnace, it's either because it no longer detects ignition—such as that seen above—or because of a fault with the sensor.

What is the furnace flame sensor?

In a gas furnace, the flame sensor is a device that controls the valve emitting gas or propane into the furnace’s combustion chamber. The thermal-sensitive sensor activates and closes that valve in the absence of a flame—if the furnace is not igniting the fuel, this means that the valve is releasing excess gas into your home. A properly working flame sensor is a crucial safety device that protects both the furnace and your home.

The device itself is a small metal rod that protrudes into the combustion chamber and features a heat-resistant porcelain end piece. It is connected to the rest of the gas furnace assembly by a wire, which it uses to control the gas release valve.

What are the signs of trouble?

The most common sign of a problem with the furnace flame sensor is the entire system shutting itself off. When a faulty sensor no longer detects a flame—even if the system is igniting normally—it will cut off the supply of gas or propane, shutting the system down. In the event that a furnace has stopped working and there isn’t another explanation (such as a power outage), the flame sensor is typically one of the first things our HVAC technicians will take a look at.

In a worst-case scenario, a malfunctioning flame sensor can lead to excess gas building up, which has hazardous consequences:

  • Carbon Monoxide: If the gas is able to escape from the furnace through the valve and accumulates, it could lead to the buildup of carbon monoxide—a toxic gas that is colorless and odorless.
  • System Damage: If the gas builds up inside of the furnace combustion chamber or escapes from it, it could cause an explosion when it meets an open flame, such as the pilot light on a gas water heater or inside of a stove.

What are the common flame sensor issues?

There are two common issues that can lead to a furnace’s flame sensor not working correctly:

1. The flame sensor is dirty or corroding

As your furnace experiences regular use throughout the winter months, black soot or burnt carbon material can build up on the flame sensor, impacting its ability to properly sense if the furnace is properly igniting. One of the major benefits of a professional gas furnace tune-up is that our technicians clean the flame sensor thoroughly, polishing it so that it continues to work as expected.

2. The sensor is cracked or damaged

Your gas furnace will most likely outlive at least one of its flame sensors. The heat the sensor is exposed to can cause it to break. In most cases, the porcelain end cracks or shatters. Or, the wiring connecting the sensor to the main body of the furnace is damaged. In either scenario, the entire sensor will need to be replaced. This is a job we recommend leaving to one of our HVAC professionals: many makes and models of gas furnaces have their own specific flame sensor, so it’s important to make sure the right one is ordered and then installed correctly.

Call our team for 24/7 gas furnace repair here in Baton Rouge

If your furnace has stopped working, have one of the NATE-certified technicians at Buddy's Air Conditioning & Heating out to inspect your system, diagnose the problem, and apply a fix. We offer 24/7 emergency service here in Baton Rouge, which means you and your family don’t have to go without heating this winter.

If you suspect that your flame sensor or another component is faulty, let us know. Our team specializes in gas (and electric!) furnace repair, and we can get your system back up-and-running again—fast. Contact us online, or give us a call at 225-749-2169.