Typical Components that Fail on a Furnace

Furnaces are one of the most expensive systems inside your home. They can cost thousands of dollars to install, and account for almost one-third of your monthly utility bills.

Furnaces have one job – they warm the air and deliver it to every room in your home. A modern gas furnace will have dozens of components that all work together to get the job done. 

During the winter, your furnace may turn on and off dozens of times. That can put a lot of strain on the individual components. And while all parts can fail on a furnace, replacing them might not make sense, depending on the furnace’s age. 

HVAC technicians have a general rule of thumb: replacement is a better path if the repair cost multiplied by the furnace’s age is more than $5,000.  

Still, it’s worth a little investigation to understand how your home’s heating system works. Here are the components that fail most often. 

Ignition System

The ignition system powers the furnace. If the ignition system fails, your furnace won’t be able to produce heat. There are two types of ignition systems: pilot and electronic. Pilot ignition systems use a continuously burning flame to ignite the fuel, while electronic ignition systems use an electric spark. Common causes of ignition system failure include a faulty thermocouple, a worn-out spark igniter, or a malfunctioning control board.

Heat Exchanger

The heat exchanger transfers heat from the combustion chamber to the air circulating through your home. If the heat exchanger fails, your furnace won’t be able to produce warm air. The most common cause of heat exchanger failure is prolonged exposure to high temperatures, which can cause cracks and leaks. It’s one of the most expensive repairs, and because it usually happens with age and wear and tear, it’s also an indicator that it’s time to replace your furnace.  

Blower Motor

The blower motor circulates the heated air throughout your home. If the blower motor fails, you won’t get warm air from your furnace. Common causes of blower motor failure include worn-out bearings, a faulty capacitor, or a malfunctioning control board.

Control Board

The control board is the brain of the furnace, responsible for managing all of its functions. If the control board fails, your furnace won’t be able to function correctly. Common causes of control board failure include power surges, corrosion, and normal wear and tear.

Flame Sensor

The flame sensor is responsible for detecting whether the furnace has successfully ignited. If the flame sensor fails, your furnace may not be able to start or may shut down shortly after starting. Common causes of flame sensor failure include corrosion, dirt buildup, or a broken wire.

Gas Valve

The gas valve controls the flow of gas to the furnace. If the gas valve fails, your furnace won’t be able to produce heat. Common causes of gas valve failure include a faulty solenoid, a worn-out diaphragm, or a malfunctioning control board.

What’s going on with your furnace? Do you suspect a component has failed? 

Any of the components listed above can fail, causing your furnace to stop working correctly. If you suspect that your furnace has a problem, it’s essential to contact a professional HVAC technician to diagnose and repair the issue promptly.