How Can You Tell If You Have a Faulty Furnace Ignitor?

Because natural gas doesn’t possess any latent heat, gas furnaces require an ignition system to combust the gas and create heat for your home. Your furnace ignitor is a key component that ensures gas furnaces run safely and efficiently. If the ignitor is damaged or malfunctioning, your furnace can function poorly or in some cases not at all. How do you tell if your furnace ignitor is faulty? 

Figuring out the problem depends on the type of furnace ignitor you have. While old furnaces may have a standing pilot light, electronic ignitors are the most common type for modern gas furnaces. We’ll review the differences in each type as well as how a faulty ignitor affects your furnace and what components can keep the ignitor from working. 

What Is a Furnace Ignitor? 

Your furnace ignitor is a key component in the heating cycle. It provides the heat needed to combust the furnace’s natural gas supply. This heat is exchanged into the HVAC system’s air handler before flowing into your ductwork. Without the furnace ignitor, your heating may as well be an expensive fan. 

Older furnaces used to have a standing pilot light to keep the gas lit. This tiny flame would remain lit even between heating cycles. Modern furnaces have transitioned to an electronic ignition system, and these ignitors are safer and more energy efficient. The two most popular types of electronic furnace ignitor are: 

  • Direct spark ignitor – These ignitors use a high-voltage spark to light a pilot flame, which then heats the natural gas. Unlike traditional pilot lights, these flames are only active during the heating cycle. Once the furnace is finished running, both the spark ignitor and the pilot flame are turned off.
  • Hot surface ignitor – A hot surface ignitor resembles the filament wire in a light bulb. An electric current heats a small piece of metal until it’s hot enough to combust the gas. Hot surface ignitors are typically the most common type of ignition system in modern gas furnaces. 

Your furnace likely has one of these electronic ignitors. Since they’re housed inside the furnace, damage or component failure isn’t always obvious. Instead, the furnace might stop running like it is supposed to. This is often the initial sign you have a faulty furnace ignitor. 

You Might First Notice Problems with How the Furnace Runs 

A faulty furnace ignitor can impact normal operation in multiple ways. These range from stopping the furnace from running entirely to constant cycles of starting and stopping. Have you noticed your furnace malfunctioning in any of the following ways? 

The furnace won’t start: Combusting natural gas can be hazardous, namely if a component of the furnace isn’t working properly. When the ignitor is malfunctioning, safety features will stop the furnace from running entirely to prevent further damage or additional problems. 

The furnace blows cool air: Unheated air coming through your ductwork is a clear sign something is malfunctioning. The furnace might not recognize that the ignitor is malfunctioning and other components like the air handler will work as normal. 

The furnace is short cycling: This annoying problem means the furnace’s heating cycles are too short or repetitive. Not only will it be inadequate for heating your home, but it places extra strain on the furnace itself. Short cycling can occur when the furnace ignitor flips on and off, which activates the safety features and shuts the furnace off. 

Other Components Can Stop the Ignitor from Working 

In other cases, the ignitor won’t work because another element of your furnace is malfunctioning. When making a furnace repair call, professional technicians in the U.S. might review the following components as well: 

  1. Air filter: Furnaces need proper airflow for safe operation. A clogged air filter can result in the furnace overheating, and safety features will stop the ignitor from turning on. 
  1. Drain pan: Despite the fact a furnace creates heat, some condensation can still be found. A full drain pan will stop the ignitor from running to keep the pan from overflowing and causing water damage within the furnace. 
  1. Flame sensor: This safety component ensures the gas valve is only open when the ignitor is working. If the flame sensor is dirty, it can incorrectly believe the ignitor isn’t on. 
  1. Circuit breaker: Since the majority of ignition systems are electronic, many technicians will inspect the circuit breakers first. When resetting the breaker doesn’t resolve the issue, a more complex electrical problem is likely present. 
  1. Gas supply or valve: The click sound you hear when the furnace starts is the gas valve opening. A problem with the furnace’s gas supply or the valve itself can stop the ignitor from starting. This fail-safe prevents gas from continuously leaking into the furnace or the rest of your home. 

Here’s How Technicians Identify a Faulty Furnace Ignitor 

Calling a professional technician for furnace repair in the U.S. is the fastest way to resolve a problem with the furnace ignitor. They’ll have the tools and training to narrow down likely causes and can start with the most obvious culprits. Over the course of diagnostics, the technician may try several things, including: 

  • Inspecting the thermostat and circuit breaker first: It’s always a relieving surprise when fixing the problem is as simple as resetting the thermostat or circuit breaker. Even if these things don’t work, inspecting them can help the technician determine if the problem is electrical in nature. 
  • Looking for the ignitor’s glow or obvious signs of damage: Cracks or missing pieces are easy to spot, just like the glow from a direct spark or hot surface ignitor. Experts can rule out other problems more easily this way. 
  • Test the ignitor’s voltage or electrical resistance: If the problem is electrical, testing the ignitor with a voltage or multimeter can offer more definitive proof you have a faulty furnace ignitor. 

How Much Does Furnace Ignitor Replacement Cost? 

Costs can vary depending on the model of both the furnace and the electronic ignitor. With parts and labor, homeowners can expect to spend an average of $100 to $350 on replacement costs. The average life span of the furnace ignitor is seven7 years, so in some cases the issue is a result of the ignitor simply becoming too old to function properly. Whatever the problem is, a certified technician can find the source and offer the most cost-effective solutions. 

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