Furnace Ignitor: Understanding its Function and Importance
A furnace including the hot surface ignitors used in many Carrier gas furnaces, is the component responsible for lighting the fuel in your heating system to create heat. Without a functioning ignitor, the burners cannot light, and your furnace will not produce warmth. Carrier gas furnace models, including Infinity® furnaces, use Silicon Nitride Power Heat™ hot surface ignitors designed to provide reliable electronic ignition.
This guide explores how furnace ignitors work, signs of failure, and essential tips for maintenance and troubleshooting.
How Does a Furnace Ignitor Work?
A Carrier furnace ignitor initiates combustion by creating enough heat or a spark to ignite the gas entering the burner assembly. Once the thermostat signals a need for heat, the ignitor activates, lighting the fuel to warm the air that circulates through your home.
For a Carrier furnace equipped with a hot surface ignitor, electrical current heats the ignitor element until it glows and can ignite the gas. Carrier uses silicon nitride hot surface ignitors in several of its gas furnace models.
Why Is The Furnace Ignitor Important?
Daniel Donahue, general manager of Mullen Refrigeration Service in Latrobe, Pennsylvania, explains why the furnace ignitor is an important component of today's heating systems.
"Modern furnaces rely on a component called a hot surface ignitor to safely and efficiently light the burners when heat is needed," Donahue said." Older heating systems often used standing pilot lights, which continuously burned a small amount of gas whether the furnace was actively heating the home or not. While effective, that approach consumed fuel year-round, even during months when the heating system wasn't in use."
"Today's hot surface ignitors operate much more efficiently. When the thermostat calls for heat, the ignitor heats up and glows. The gas valve then opens, and the fuel ignites immediately. Because the furnace only burns fuel when it's actively heating the home, the system operates more efficiently and reduces unnecessary energy consumption."
"In addition to improving efficiency, hot surface ignitors help enhance system reliability. They're designed to provide consistent ignition when the furnace starts, allowing the heating system to operate safely and effectively throughout the heating season."
"While the ignitor is a relatively small component, it plays a critical role in the furnace's operation. Without it, the system can't ignite the burners and produce heat. That's why routine maintenance and inspections are important for ensuring the ignitor and other key components remain in proper working condition."
Common Types of Igniters for Furnace Systems
Different furnaces use different ignition technologies. The three most common types are:
- Hot Surface Ignitors: Carrier uses silicon nitride hot surface ignitors in several of its modern gas furnace models. These ignitors work like a lightbulb filament. When electricity flows through, the element heats up and glows to ignite the gas. Carrier also documents silicon carbide as another common hot surface ignitor material.
- Spark Ignitors: These use a high-voltage electric spark to light the gas, similar to a spark plug in a car or a gas grill starter. The exact voltage and electrical specifications depend on the furnace and ignition system.
- Intermittent Pilot Ignitors: These use an electric spark to light a small pilot flame only when heat is needed, rather than keeping a pilot light burning constantly.
Carrier Furnace Ignitor Comparison
| Ignitor Type | Material/Technology | Typical Application | Key Consideration |
|---|---|---|---|
| Hot Surface Ignitor | Silicon nitride or silicon carbide | Modern gas furnaces | Heats until it glows and ignites the gas |
| Spark Ignitor | Electrode and spark gap | Furnaces using electronic spark ignition | Creates a spark to ignite the fuel |
| Intermittent Pilot Ignitor | Electronic spark ignition | Furnaces using intermittent pilot systems | Ignites a pilot flame only when heat is needed |
Carrier's published specifications demonstrate why voltage and resistance should be checked against the specific furnace model rather than treated as universal ignitor specifications. For example, one Carrier silicon-nitride furnace specifies a 102–132 VAC operating range and a new ignitor resistance of 40–70 ohms at room temperature.
How to Identify a Faulty Furnace Ignitor
A faulty furnace ignitor is often the reason a furnace stops producing heat. If the ignitor cannot light the gas, the system’s safety features will shut the furnace down and prevent the heating sequence from continuing.
Warning Signs of Failure
- No Heat: The furnace blower runs, but the air isn't warm.
- Short Cycling: The furnace turns on and off frequently without reaching the set temperature.
- No Glow: For hot surface ignitors, you don't see the characteristic orange glow during the ignition sequence.
- Clicking Sounds: You hear repeated clicking from a system using spark ignition as it attempts to ignite the fuel.
Common Causes of Damage
- Wear and Tear: Ignitors are fragile and operate at extreme temperatures, naturally degrading over time.
- Power Surges: Electrical fluctuations can burn out the heating element.
- Contamination: Dirt, dust, or oils (even from fingerprints) on the surface can create hot spots that cause the component to crack.
Because ignitor life varies by furnace model, operating conditions, and heating cycles, Carrier does not specify one universal replacement interval for all furnace ignitors. Carrier notes that smaller furnace components such as igniters may require replacement sooner than major components because of normal wear and tear.
Furnace Ignitor Maintenance
Routine furnace maintenance is the best way to extend the life of your ignition system. When you schedule furnace service with a local Carrier dealer, they typically perform the following checks:
- Safety Check: Power is turned off to ensure safe inspection.
- Gentle Cleaning: Technicians carefully remove dust or carbon buildup. Note: Homeowners should avoid touching the ignitor element, as oils from skin can shorten its lifespan.
- Resistance Testing: Using a multimeter, they measure electrical resistance and compare the reading with the furnace manufacturer's specifications. Carrier documentation, for example, provides model-specific resistance ranges for its silicon-nitride ignitors.
Furnace Ignitor Troubleshooting
If you suspect furnace ignitor repair is needed, here is how a professional diagnoses the issue.
- Visual Inspection: Looking for white spots, cracks, or breaks in the ceramic or silicon element.
- Electrical Test: Checking voltage to ensure the ignitor is receiving power and checking resistance (Ohms) to ensure the element isn't "open" or broken. The correct voltage and resistance values vary by furnace model, so technicians should use the applicable Carrier product documentation when servicing a Carrier furnace.
- Code Reading: Modern furnaces often flash an LED error code or display a diagnostic code that can indicate an ignition failure.
For more details on resolving heating issues, view our guide on furnace troubleshooting.
Connect With Your Carrier Dealer For Your Furnace Ignitor Needs
While some homeowners attempt DIY furnace repairs, the furnace ignitor is a delicate and high-voltage component. Incorrect installation can lead to immediate failure or safety risks. For reliable results and to protect your warranty, consult your local Carrier dealer for professional gas furnace ignitor service.
Carrier recommends professional service for furnace repairs involving gas lines, electrical components, or internal furnace components because of the potential for gas leaks, electrical hazards, and carbon monoxide exposure.
Frequently Asked Questions
To reset a furnace ignitor, turn off the power to the furnace at the breaker and the gas supply valve. Wait 5-10 minutes for safety lockouts to clear, then turn the power and gas back on. If the unit still fails to light, call a professional.
A furnace ignitor typically costs between $20 and $150 for the part itself. Professional replacement, which ensures safety and proper handling, usually brings the total cost to between $150 and $450, depending on your location and furnace model.
Failures are usually caused by normal wear from high-heat cycles, power surges, or contamination. Touching the heating element with bare hands during installation can leave oils that cause the part to overheat and shatter prematurely.
Common symptoms include the furnace blowing cold air, short cycling, or the absence of an orange glow during the startup sequence. If your furnace clicks but never roars to life, the ignitor is a likely culprit.
While possible, DIY replacement is risky. Ignitors are extremely fragile, and improper handling can break the new part immediately. Additionally, working with high-voltage electricity and gas components requires safety precautions best handled by a certified HVAC technician.
About The Author: Ryan Mayes is a Senior Digital Brand Marketing Manager at Carrier who focuses on creating clear, helpful resources on HVAC topics. Ryan’s goal is to guide readers toward smart, confident decisions about their indoor comfort.
About The Expert Reviewer: Seth Faber is a Product Manager for Residential Furnaces at Carrier Corporation, where he helps develop dependable, high-performance heating solutions that deliver reliable comfort while meeting evolving homeowner needs, energy efficiency standards, and industry regulations.