Because natural gas doesn’t聽have聽any latent heat, gas furnaces聽use聽an ignition system to combust the gas and聽generate聽heat for your home. Your furnace ignitor is聽a vital聽component that ensures gas furnaces聽function聽safely and efficiently. If the ignitor is damaged or malfunctioning, your furnace聽could聽function聽poorly or in聽some聽cases not at all. How聽can聽you tell if your furnace ignitor is faulty?
Figuring out聽the problem depends on the聽model聽of furnace ignitor you have. While old furnaces聽can聽have a standing pilot light, electronic ignitors are the most聽likely聽type for modern gas furnaces. We’ll聽compare聽the differences in each type as well as how a faulty ignitor聽impacts聽your furnace and what components can聽keep聽the ignitor from working.
What Is a Furnace Ignitor?
Your furnace ignitor is a key component in the heating聽process. It provides the heat聽needed聽to combust the furnace’s natural gas supply. This heat is聽exchanged聽into the HVAC system’s air handler before聽moving聽into your ductwork. Without the furnace ignitor, your heating聽might聽as well be an expensive fan.
Older furnaces used to have a standing pilot light to keep the gas聽ignited. This聽small聽flame would remain lit even between heating cycles. Modern furnaces have聽moved on聽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聽-聽These ignitors聽implement聽a high-voltage spark to light a pilot flame, which then heats the natural gas.聽Unlike聽traditional pilot lights, these flames are only聽active聽during the heating cycle. Once the furnace is finished聽running, both the spark ignitor and the pilot flame are聽turned聽off.
- Hot surface ignitor聽-聽A hot surface ignitor聽resembles聽the filament wire in a light bulb. An electric current heats a small piece of metal until it’s hot enough to聽combust聽the gas. Hot surface ignitors are聽typically聽the most common type of ignition system in聽today's聽gas furnaces.
Your furnace聽likely聽has one of these electronic ignitors. Since they’re聽housed聽inside the furnace, damage or component failure isn’t always聽obvious. Instead, the furnace聽may聽stop running like it聽does normally. This is often the聽first聽sign you have a faulty furnace ignitor.
You Might First Notice Problems with How the Furnace Runs
A faulty furnace ignitor can聽disrupt聽normal operation in聽multiple聽ways. These range from聽stopping聽the furnace from running entirely to constant cycles of starting and stopping. Have you noticed your furnace聽malfunctioning聽in any of the following ways?
The furnace won’t start:聽Combusting natural gas can be hazardous,聽especially聽if a component of the furnace isn’t聽operating聽properly. When the ignitor is malfunctioning, safety features will聽keep聽the furnace from running entirely to prevent further damage or聽new聽problems.
The furnace blows cool air:聽Unheated air coming through your ductwork is a聽surefire聽sign something is聽malfunctioning. The furnace聽might聽not recognize that the ignitor is malfunctioning and other components like the air handler will聽function聽as normal.
The furnace is short cycling:聽This聽annoying聽problem means the furnace’s heating cycles are too short or repetitive. Not only will it be inadequate for heating your home, but it聽results in聽extra strain on the furnace itself. Short cycling can聽happen聽when the furnace ignitor聽turns聽on and off, which activates the safety features and shuts the furnace off.
Other Components Can聽Keep聽the Ignitor from Working
In other cases, the ignitor won’t work because another聽component聽of your furnace is malfunctioning. When making a furnace repair call, professional technicians in聽the U.S.聽might聽inspect聽the following components as well:
- Air filter: Furnaces聽require聽proper airflow for safe operation. A clogged air filter can聽lead to聽the furnace overheating, and safety features will stop the ignitor from聽kicking in.
- Drain pan: Despite the fact a furnace聽creates聽heat, some condensation can still be聽found. A full drain pan will stop the ignitor from running to keep the pan from overflowing and causing water damage聽inside聽the furnace.
- Flame sensor: This safety component ensures the gas valve is only open when the ignitor is聽running. If the flame sensor is dirty, it can聽incorrectly聽believe the ignitor isn’t on.
- Circuit breaker: Since聽the majority of聽ignition systems are electronic, many technicians will聽check聽the circuit breakers first. When resetting the breaker doesn’t聽resolve聽the issue, a more complex electrical problem is likely聽the culprit.
- 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聽keep聽the ignitor from starting. This fail-safe prevents gas from聽continuously聽leaking into the furnace or the rest of your home.
Here’s How Technicians聽Identify聽a Faulty Furnace Ignitor
Calling a professional technician for furnace repair in聽the U.S.聽is the聽best聽way to聽solve聽a problem with the furnace ignitor. They’ll have the tools and training to narrow down聽possible聽causes and can start with the most聽obvious聽culprits. Over the course of diagnostics, the technician may聽try聽several things, including:
- Inspecting the thermostat and circuit breaker first: It’s always a聽relieving聽surprise when fixing the problem is as聽simple聽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聽spot, just like the glow from a direct spark or hot surface ignitor. Experts can rule out other problems more聽quickly聽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聽evidence聽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聽can聽expect to spend聽an average of聽$100 to $350 on replacement costs. The average life span of the furnace ignitor is 7 years, so in some cases the聽problem聽is a result of the ignitor simply becoming too old to function聽correctly. Whatever the problem is, a certified technician can find the source and offer the most cost-effective solutions.
