From field experience, a failed ignitor generates more unnecessary service calls than any other single furnace problem. The part itself runs $20 to $80. Most homeowners who’ve confirmed the diagnosis complete the repair in under 30 minutes.
When a furnace runs through its startup cycle without producing heat, the ignitor is almost always where to look first. It’s the component responsible for lighting the gas burners. When it fails, your furnace cycles through its sequence repeatedly without warming a single room.
The repair requires no certifications and no gas line work. We’ve watched homeowners complete it in under 20 minutes once they’ve confirmed the diagnosis and sourced the right part. This guide walks you through every step.
To understand how an ignitor fits into a furnace’s broader operation, Wikipedia provides a solid technical overview of residential furnace systems.
TL;DR Quick Answers
A furnace ignitor replacement costs $150 to $300 with a professional, or as little as $20 to $80 in parts for a confident DIYer. You’ll know the ignitor is failing when your furnace completes its startup cycle and you hear the draft inducer run, but the burners never light and no heat reaches your vents. Most homeowners can replace a hot surface ignitor in under 30 minutes using basic tools, no certifications required.
Top Takeaways
- A bad furnace ignitor ranks among the most common causes of a furnace that runs but produces no heat
- Modern gas furnaces use hot surface ignitors, either silicon carbide (older, more fragile) or silicon nitride (newer, more durable)
- DIY part costs run $20 to $80 professional replacement typically totals $150 to $300 including labor. The most reliable symptom is a furnace that cycles through its startup sequence without the burners ever igniting
- A clogged air filter is one of the most overlooked causes of ignitor burnout, triggered by repeated furnace overheating
- If your furnace is 15 or more years old, a failing ignitor may signal a broader system issue worth a professional evaluation
Table of Contents
What Is a Furnace Ignitor?
A furnace ignitor lights the gas burners in a modern forced-air heating system. Older furnaces relied on a standing pilot light for this job. In the vast majority of furnaces built since the early 1990s, a hot surface ignitor (HSI) replaced the pilot, improving reliability, cutting energy waste, and eliminating the need to manually relight after outages.
When your thermostat calls for heat, the furnace control board sends electrical current to the ignitor. The element heats rapidly, reaching temperatures between 1,800°F and 2,500°F, hot enough to ignite the gas flowing through the burners. The full ignition sequence completes in roughly 30 to 60 seconds.
Two types of hot surface ignitors are standard in residential furnaces:
- Silicon carbide ignitors: the original design, recognizable by their dark gray color. Effective but brittle. Even light physical contact or vibration can cause cracking.
- Silicon nitride ignitors: the newer standard, significantly more durable and resistant to thermal shock. More expensive than silicon carbide, but longer-lasting under normal operating conditions.
Knowing which type your furnace uses matters when sourcing a replacement. Always cross-reference your furnace’s model number before ordering a part.
Warning Signs Your Furnace Ignitor Is Failing
Ignitor failure tends to announce itself in consistent, recognizable ways. Knowing what to look for saves time and avoids paying for a service call you don’t need.
Furnace won’t ignite at all
The furnace powers on, the draft inducer motor runs, but the burners never light. This is the most direct symptom of a failed ignitor. The ignition sequence initiates, but nothing happens at the burner stage. The system may lock out after several failed attempts and require a manual reset.
Furnace cycles but produces no heat
The system runs through its startup sequence repeatedly, sometimes with a brief attempt at ignition, but the burners don’t sustain a flame and no warm air reaches your vents. The furnace may short-cycle, shutting off and restarting frequently, as the control board attempts and fails to confirm ignition.
You hear clicking but the burners don’t light
That clicking sound is the control board sending voltage to the ignitor and attempting to prove ignition. When clicking never results in visible flame or measurable heat output, the ignitor or gas valve is the likely culprit. A multimeter resistance test, covered in the troubleshooting section below, helps isolate which one.
Furnace keeps short-cycling
A furnace that starts, runs briefly, and shuts off before reaching the set temperature — repeating this pattern — may be detecting a failed ignition attempt and locking out as a safety measure. Short-cycling also points to the ignitor when accompanied by an ignition fault code on the control board.
Visible cracks or damage on the ignitor
With power completely off, inspect the ignitor directly. Look for hairline cracks in the element, a broken ceramic body, or heavy discoloration beyond normal tan-to-gray aging. Silicon carbide ignitors are especially prone to cracking from vibration or accidental contact. A visually damaged ignitor is not repairable. It needs replacement.
Furnace Ignitor Troubleshooting Before You Replace
Before ordering a part, work through these diagnostic steps. Not every “furnace won’t heat” situation turns out to be the ignitor, and ruling out simpler causes saves both time and money.
Check the thermostat settings
Confirm the thermostat is set to HEAT mode and that the temperature setpoint is above the current room temperature. This sounds too basic to mention, but from hands-on experience, incorrect thermostat settings account for more service calls than most homeowners expect. Check it first, every time.
Inspect and replace the air filter
A severely clogged air filter restricts airflow through the furnace. When airflow is blocked, the heat exchanger overheats. Repeated overheating degrades the ignitor faster, and in some cases a single severe overheat is enough to crack a silicon carbide element.
Replacing a dirty filter is a zero-cost diagnostic step with real consequences for ignitor longevity. Filterbuy offers a wide selection of replacement filters sized for most residential systems, and keeping a clean filter in place is one of the most effective ways to protect your ignitor and extend your furnace’s working life.
Affiliate Disclosure: HVACGuidePost.com may earn a commission on qualifying Filterbuy purchases at no additional cost to you.
Test ignitor resistance with a multimeter
A resistance test is the most reliable way to confirm ignitor failure before buying a replacement part. With the furnace powered off and the ignitor wire harness disconnected:
- Set your multimeter to the resistance (Ω) setting
- Touch the probes to both terminals on the ignitor connector
- A healthy silicon carbide ignitor typically reads 40 to 90 ohms; silicon nitride reads lower, usually 10 to 20 ohms
- An OL (open loop) or infinite resistance reading confirms the element has failed
Consult your furnace manufacturer’s documentation for the specific resistance range for your model, as values vary by brand and ignitor design.
Check for error codes on the control board
Most furnaces built after 2000 display diagnostic fault codes through a flashing LED on the control board. These codes correspond to specific failure modes. The code chart is typically printed on a sticker inside the furnace cabinet door, or listed in your owner’s manual. An ignition failure code confirms your diagnosis before you spend a dollar on parts.
Furnace Ignitor Replacement Cost
Cost is one of the first questions homeowners ask, and the answer depends primarily on whether you complete the repair yourself or hire a professional.
DIY replacement cost
The ignitor part itself is the primary expense. Replacement hot surface ignitors typically range from $20 to $80 depending on the furnace brand, ignitor type, and sourcing. OEM (original equipment manufacturer) parts run higher; compatible aftermarket ignitors often perform comparably at lower cost. Verify part compatibility using your furnace’s model and serial numbers.
Professional replacement cost
A licensed HVAC technician typically charges $150 to $300 for an ignitor replacement, including the part and labor. Emergency or after-hours service calls carry a premium, often $75 to $150 above standard rates. Diagnostic fees may apply separately depending on the company’s billing structure.
DIY vs. professional — cost comparison
- Part cost: DIY $20 to $80 | Professional: included in total
- Labor cost: DIY $0 | Professional: $100 to $200
- Total estimate: DIY $20 to $80 Professional: $150 to $300
- Time required: DIY 20 to 30 minutes | Professional: scheduled visit
- Skill level: DIY moderate | Professional: N/A
Factors that affect cost
- Furnace brand and age: proprietary OEM ignitors for premium brands cost more and may be harder to source
- Ignitor type: silicon nitride ignitors cost more than silicon carbide but last longer
- Local labor rates: HVAC labor costs vary significantly by region
- Emergency service: after-hours or weekend calls typically add a $75 to $150 surcharge
- Diagnostic fees: some technicians charge a service call fee separate from the repair estimate
How to replace a furnace ignitor — step by step
Most homeowners comfortable with basic home repairs can handle this job. The process is straightforward. The one non-negotiable rule is to never touch the ignitor element with bare hands.
Tools needed: Screwdriver (¼-inch hex or Phillips, depending on furnace brand), needle-nose pliers, multimeter, work gloves, smartphone for photos.
Safety first
Turn off power at the circuit breaker, not at the furnace power switch alone. Also close the gas shutoff valve on the supply line near the furnace. Allow the unit to cool completely before opening any panels.
If you detect a gas odor at any point, stop work immediately. Leave the home without operating any switches and call your gas utility’s emergency line.
Steps
- Turn off power at the breaker. Locate your electrical panel and flip the furnace circuit to OFF. Verify with a non-contact voltage tester if you have one.
- Close the gas supply. Locate the shutoff valve on the gas supply line near the furnace. Turn the handle perpendicular to the pipe to close it.
- Allow the furnace to cool. Wait at least 30 minutes after the last heating cycle before opening the cabinet.
- Remove the access panel. Take off the front access panel, typically secured by screws or a slide-and-lift latch.
- Locate the ignitor. The hot surface ignitor sits near the burner assembly. It’s a small, fragile component, usually L-shaped or flat, connected to a wire harness.
- Photograph everything before disconnecting. Take clear photos of the wiring connections and the ignitor’s mounting position. This step prevents reassembly errors.
- Disconnect the wire harness. Gently squeeze the connector tab and pull the harness free. Pull on the connector, never on the wires themselves.
- Remove the mounting screws. Typically one or two screws secure the ignitor bracket. Keep them. You’ll reuse them with the new ignitor.
- Install the new ignitor carefully. Handle the new ignitor only by its ceramic base or mounting bracket. Never touch the silicon carbide or silicon nitride element with bare skin. Skin oils create hot spots that cause premature failure. Secure the mounting screws snugly. Don’t overtighten.
- Reconnect the wire harness. Click the connector firmly into place.
- Replace the access panel and confirm it’s fully seated.
- Restore gas and power. Open the gas shutoff valve (handle parallel to the pipe), then flip the furnace circuit breaker back to ON.
- Test the furnace. Set the thermostat above current room temperature and initiate a heating cycle. Observe the startup sequence. The ignitor should glow visibly orange-red within 30 to 60 seconds, followed by burner ignition and warm air reaching your vents.
When to call a professional instead
DIY ignitor replacement works for most confident homeowners. Some situations call for a licensed HVAC technician:
- The furnace is 15 or more years old. A failing ignitor at this age may signal broader system decline. A technician can assess whether a repair or full replacement makes better financial sense.
- The ignitor has failed more than once in the past two heating seasons. Repeat failures point to a root cause that a new ignitor won’t solve: airflow restriction, control board issues, or an oversized system.
- You detect any gas odor. Leave the home immediately, avoid operating any switches or open flames, and call your gas utility’s emergency line.
- The furnace displays a heat exchanger fault code. A cracked heat exchanger is a safety concern requiring professional evaluation. It’s not a DIY repair.
- You’re not confident working around gas appliances. Calling a licensed technician is the right call when any doubt exists. There’s no value in pushing through uncertainty on a gas-fired appliance.
“In nearly every case where a homeowner replaced their furnace ignitor twice in three years, the real culprit was a filter that hadn’t been changed in months — the overheating cycle burned through both ignitors, and no one looked at the filter until the third call.”
Essential Resources
The following resources come from authoritative .gov and .org sources. Each supports the guidance on this page.
Wikipedia — Furnace https://en.wikipedia.org/wiki/Furnace A technical overview of residential furnace types, operation, and components, useful for understanding where the ignitor fits in the broader heating system.
U.S. Environmental Protection Agency — Indoor air quality https://www.epa.gov/indoor-air-quality-iaq EPA’s hub for indoor air quality guidance, including the role of HVAC maintenance in maintaining healthy indoor air. Supports the filter maintenance connection to ignitor longevity.
ENERGY STAR — Heating and cooling https://www.energystar.gov/products/heating_cooling ENERGY STAR program guidance on efficient heating equipment. Relevant to homeowners evaluating whether to repair an aging furnace or invest in a higher-efficiency replacement.
U.S. Consumer Product Safety Commission — Carbon monoxide information center https://www.cpsc.gov/Safety-Education/Safety-Education-Centers/Carbon-Monoxide-Information-Center CPSC safety guidance on carbon monoxide hazards in the home, essential context for the gas appliance safety notices in the step-by-step section.
American Lung Association — Indoor air pollutants and health https://www.lung.org/clean-air/indoor-air American Lung Association guidance on indoor air quality and the health impacts of combustion appliances and poor filtration, supporting the filter maintenance and HVAC upkeep guidance throughout this page.
Supporting Statistics
Statistic 1 Heating accounts for approximately 45% of a home’s total energy bill. Source: U.S. Department of Energy — Furnaces and Boilers https://www.energy.gov/energysaver/furnaces-and-boilers
A malfunctioning ignitor that causes repeated incomplete cycles or system lockouts wastes money on energy costs on top of lost comfort. That 45% makes furnace efficiency one of the highest-impact maintenance priorities in any home.
Statistic 2 A properly maintained gas furnace has an average service life of 15 to 20 years. Source: U.S. Department of Energy — When to Replace Heating and Cooling Equipment https://www.energy.gov/energysaver/when-replace-heating-and-cooling-equipment
Furnace age drives the repair-vs.-replace decision more than any other single factor. An ignitor replacement on a 5-year-old furnace is a straightforward call. The same repair on a 17-year-old unit warrants a broader conversation about system reliability and long-term efficiency.
Statistic 3 Americans spend approximately 90% of their time indoors, where air pollutant concentrations can be 2 to 5 times higher than typical outdoor levels. Source: U.S. Environmental Protection Agency — Indoor Air Quality https://www.epa.gov/report-environment/indoor-air-quality
A functioning furnace with a clean filter does more than heat your home. It actively circulates and filters the indoor air your household breathes every day. Ignitor failure stops that process entirely, making timely repair both a comfort and an air quality issue.
Final Thoughts and Opinion
Furnace ignitor replacement sits in a rare category of HVAC repairs: significant enough to matter, accessible enough for most homeowners to handle themselves. A $30 part and 30 minutes of careful work can restore a fully functional heating system. That’s worth knowing.
That said, treat every ignitor failure as a diagnostic prompt, not a parts-swap. What caused it? How old is the furnace? When was the last filter change? A cracked silicon carbide element might result from a single bad vibration — or it might be the fourth symptom of a furnace running harder than it should for the past two years.
The filter connection deserves particular attention. From field experience, the link between neglected filters and ignitor burnout is one of the most underappreciated relationships in residential HVAC. A $15 filter change at the right time can extend ignitor life by years. That’s not a marketing claim. It’s basic thermodynamics applied to a small, fragile component running at 2,000°F.
If your furnace is under 15 years old and the ignitor is the only failure point, replace it yourself with confidence. If the furnace is older or the ignitor failure is a repeat, get a professional opinion before spending money on parts. Either way, you now have what you need to make that call clearly.
Frequently Asked Questions
How long does a furnace ignitor last?
Most hot surface ignitors last between 3 and 5 years under normal operating conditions, though well-maintained units with clean filters sometimes reach 7 years or more. Silicon nitride ignitors tend to outlast silicon carbide by a significant margin due to their greater resistance to thermal shock and vibration.
Can I replace a furnace ignitor myself?
Yes. For most homeowners comfortable with basic home repairs, this is a manageable DIY project. Power off both the electricity and gas supply before starting, never touch the ignitor element with bare hands, and confirm part compatibility with your furnace’s model number. The job typically takes 20 to 30 minutes.
What causes a furnace ignitor to fail?
The most common causes are age and thermal stress, physical cracking (especially in silicon carbide models), and overheating caused by restricted airflow, typically from a clogged air filter. Control board issues that send incorrect voltage to the ignitor can also cause premature failure, as can power surges.
How do I test a furnace ignitor?
Use a multimeter set to resistance (Ω). With the furnace powered off and the ignitor disconnected, touch the probes to both ignitor terminals. A healthy silicon carbide ignitor reads roughly 40 to 90 ohms; silicon nitride reads 10 to 20 ohms. An OL (open loop) reading means the element has failed and needs replacement. Always confirm the expected resistance range for your specific model.
Is a cracked furnace ignitor dangerous?
A cracked ignitor fails to ignite the gas burners. Your furnace won’t heat, and the crack itself doesn’t trigger a gas release. A furnace that repeatedly attempts ignition without success should be addressed promptly. If you detect any gas odor during or after startup attempts, shut off gas, leave the home, and call your gas utility immediately.
Will a bad ignitor cause my furnace to short-cycle?
Yes. When the ignitor fails to initiate combustion, the furnace control board detects the failed ignition attempt and shuts the system down as a safety measure. The thermostat then triggers another startup attempt, creating a short-cycle pattern. A furnace starting and stopping repeatedly without producing heat is a reliable indicator that a failed ignitor is worth investigating.
Does replacing the air filter actually protect the ignitor?
It does, directly. A clogged filter forces the furnace to run hotter to compensate for restricted airflow, stressing the heat exchanger and repeatedly exposing the ignitor to temperatures beyond its design range. Replacing the filter on schedule is one of the most cost-effective ways to extend ignitor life and reduce overall furnace maintenance costs.
Protect Your Ignitor: Start With a Clean Filter
A clogged filter is one of the leading causes of ignitor burnout. Replacing your filter on schedule is the lowest-cost maintenance step with the highest return on furnace longevity.
Find your replacement filter at Filterbuy.