Your Furnace Won't Light.
Probably the ignitor — here's what it costs and how to be sure.
Everything you need before you call a tech or touch a wire.

Silicon carbide cracks. That's the root of most furnace ignitor failures — a thin, fragile rod that glows orange-hot hundreds of times a season eventually develops a hairline fracture you can barely see, and one morning your furnace runs through its startup cycle, nothing ignites, and the system locks out. The house gets cold. You start Googling.

This article covers what a furnace ignitor actually does, the specific symptoms that separate a dead ignitor from other cheap-fix and expensive-fix causes, what the replacement parts cost by ignitor type, what a technician charges versus what a confident DIYer pays, and the handful of situations where DIY is a genuinely bad idea. By the end, you'll know whether to order a part tonight or pick up the phone.

What a Furnace Ignitor Does — and Why It Fails So Often

Before the mid-1990s, most residential furnaces used a standing pilot light: a small, continuously burning flame that would ignite the main burner when the thermostat called for heat. Standing pilots wasted gas and could blow out in a draft. Manufacturers moved to electronic ignition, and the two dominant types you'll encounter today are the hot surface ignitor (HSI) and the spark ignitor.

Hot surface ignitors are more common in gas furnaces made after roughly 1995. The control board sends 120 volts (in older designs) or 80 volts (in newer silicon nitride designs) to the ignitor, which heats to around 2,500°F in 15 to 60 seconds. Once the control board senses the ignitor is hot, it opens the gas valve and the burner lights. The whole sequence takes under two minutes.

The fragility is baked into the physics. Silicon carbide — the older material, used by brands like Honeywell/Resideo and many OEM furnace makers through the 2000s — is electrically conductive, heats fast, and is brittle enough that touching it with bare fingers deposits skin oils that create a hot spot and accelerate cracking. Silicon nitride, used in most ignitors made after roughly 2010, is tougher and resists thermal shock better, which is why manufacturers like Robertshaw and White-Rodgers switched to it. Silicon nitride ignitors typically last 7 to 10 years; silicon carbide ones often fail in 3 to 5 years in high-cycling systems.

The failure mode is almost always a crack in the heating element. A cracked ignitor has an open electrical circuit: current can't flow, the element doesn't heat, gas doesn't ignite, the furnace locks out. Occasionally an ignitor degrades rather than cracks outright — it still glows, but not hot enough to reliably light the burner, causing intermittent ignition failures. Both scenarios produce the same complaint: the house is cold and the furnace seems to be running but producing no heat.

Symptoms That Actually Point to the Ignitor (Not Something Else)

The frustrating thing about a dead ignitor is that the symptoms overlap with a half-dozen other problems. Here's how to read what your furnace is telling you.

Classic ignitor failure pattern

• The furnace inducer motor starts and runs normally — you hear the draft blower spin up.
• After 15 to 90 seconds (the pre-purge cycle), nothing ignites. No click, no whomp, no flame.
• The furnace runs the draft blower for another minute or two, then shuts off completely.
• It may try again once or twice before locking out and flashing an error code.
• The error code on most modern furnaces (Carrier, Lennox, Trane, Goodman, Rheem) will be something like 3 flashes or a code reading "pressure switch fault" or "ignition failure" — check your furnace manual for your specific code sequence.

What it's probably NOT if you see these things

• If you hear clicking but no ignition: That's a spark ignitor system or a gas valve issue — the ignitor itself is working but something else is preventing combustion.
• If the furnace blows air but it's lukewarm, not cold: The burner is lighting but heat transfer is compromised — look at the heat exchanger or flame sensor, not the ignitor.
• If the furnace won't start at all — no motor, no sound: The problem is upstream of the ignitor: thermostat wiring, control board, transformer, or a tripped high-limit switch.
• If it works fine for an hour then quits: Classic heat exchanger crack or a failing limit switch, not the ignitor.

The five-minute multimeter test

Set your multimeter to resistance (ohms). Touch one probe to each terminal on the ignitor itself. A working silicon carbide ignitor reads 40 to 90 ohms. A working silicon nitride ignitor reads 40 to 200 ohms. If your meter reads OL, infinite, or simply won't register a number, the element is open and the ignitor is dead. This test takes the guesswork out entirely and takes five minutes. Don't skip it.

Replacement Part Costs by Ignitor Type

The part itself is rarely expensive. What you're mostly paying for when you hire a technician is the diagnostic time and the truck roll. Understanding the part market helps you have an informed conversation with whoever you call.

Silicon carbide ignitors

Universal silicon carbide ignitors from Honeywell (Q3400A series) or White-Rodgers (767A-369 series) run $18 to $35 at Home Depot, Amazon, or an HVAC supply counter like Johnstone Supply or Wittichen. OEM-specific versions — if your furnace manufacturer insists on a branded part — can run $45 to $75, mostly because of the sourcing markup, not meaningful quality difference.

Silicon nitride ignitors

These are more robust but slightly pricier. Expect to pay $25 to $55 for a universal silicon nitride ignitor from Robertshaw (41-408 or 41-413 series) or Emerson/White-Rodgers. If your Carrier, Lennox, or Trane furnace requires a specific OEM part number, a distributor may quote you $60 to $100. In most cases a compatible universal part works identically — but confirm the ohm rating and mounting bracket style match before ordering.

Spark ignitors

Less common in residential furnaces, more common in boilers and older systems. Spark electrode assemblies run $15 to $40. The more common failure in spark systems isn't the electrode itself but the ignition module that drives it — which is a different, more expensive repair ($80 to $200 for the module alone).

Furnace-specific notes

• Goodman/Amana furnaces (very common in new construction through the 2010s) use a Norton/Saint-Gobain silicon carbide ignitor. Universal replacements fit in most cases. Part cost: around $20.
• Carrier/Bryant uses a silicon nitride ignitor in post-2005 models. Carrier's OEM part (HH18HA403) lists around $50 to $70 from a Carrier distributor; compatible aftermarket versions run $30 to $45.
• Lennox has been silicon nitride since roughly 2000. The ignitor for common G60 and EL296 series furnaces (part 20-1/2" bracket style) costs $35 to $55 in the aftermarket.
• Trane/American Standard ignitors vary by model year; plan on $30 to $60 for the part.

The part price spread between buying at a big-box store and buying from an HVAC supply house is usually small — maybe $5 to $10. HVAC supply houses sometimes carry higher-quality universal kits that include the mounting hardware and wiring adapters, which can be worth the slight premium if your old bracket is corroded.

What a Technician Charges — and What You're Actually Paying For

A professional HVAC technician replacing a furnace ignitor will typically charge $150 to $300 total, all-in. That breaks down roughly as follows:

• Diagnostic/service call fee: $75 to $125, charged just to show up and identify the problem. Some companies waive this if you proceed with repair; many do not.
• Labor to replace the ignitor: 30 to 45 minutes of actual work, usually billed at $85 to $150 per hour, meaning $45 to $110 in labor.
• Part markup: Technicians typically charge 30% to 100% above their cost for parts. A $25 ignitor might appear on your invoice as $50 to $60.

So the total for a straightforward ignitor replacement — where the tech arrives, confirms the diagnosis, and swaps the part — lands between $150 and $300 in most U.S. markets. In high-cost-of-living metros (New York City, San Francisco, Boston), that ceiling can push to $350 or even $400, especially for emergency weekend calls.

Emergency or after-hours rates are the real variable. If your furnace dies at 9 PM on a January Saturday, expect a $150 to $200 surcharge on top of normal rates. That makes the same 30-minute repair cost $300 to $500. If you can safely manage one cold night — an electric space heater in a single bedroom, pipes aren't at risk — waiting until Monday morning saves real money.

When is paying for a technician clearly worth it? Three situations: First, if you can't confirm the diagnosis yourself and don't own a multimeter. Replacing an ignitor when the real problem is a cracked heat exchanger means you've spent $150 and still have a broken furnace — and potentially a dangerous one. Second, if your furnace is under warranty and DIY repair voids it (check your documentation — this varies by manufacturer and installer). Third, if the ignitor is on a furnace with a known history of cracked heat exchangers, because a tech will inspect the exchanger while they're in there, and you should know if you have that problem.

DIY Replacement: How to Do It and Where It Goes Wrong

Replacing a hot surface ignitor is one of the most beginner-accessible furnace repairs there is, assuming you've confirmed the diagnosis with a multimeter and your furnace doesn't require refrigerant handling or vent work. The job on most furnaces is: unplug the furnace, remove a panel, unplug two wires, unscrew one or two mounting screws, reverse the process with the new part. That's it.

Step-by-step for a typical forced-air gas furnace

1. Turn off power to the furnace at the disconnect switch or breaker. Do not skip this — a 120V shock from the ignitor circuit is not pleasant.
2. Turn off the gas supply at the shutoff valve near the furnace. You're not working on the gas lines, but it's good practice.
3. Remove the furnace access panel — usually just lifts off or is held by two screws. Set it aside.
4. Locate the ignitor. It sits near the burner assembly, usually mounted on a bracket with one or two screws. It looks like a small, flat, grayish or brownish rectangular element on a white or gray ceramic mount.
5. Take a photo of the wiring and mounting orientation before you touch anything.
6. Disconnect the wiring harness — most ignitors use a simple plug-in connector. Squeeze the tab and pull.
7. Remove the mounting screws (typically 1/4" hex head or a standard Phillips). Hold the ignitor carefully by the ceramic base, not the element.
8. Install the new ignitor in reverse order, again touching only the base and connector.
9. Restore power and gas, then run the furnace through a full cycle to confirm ignition.

Where DIY fails

The most common DIY mistake is buying the wrong part. Universal ignitors come in different mounting hole spacings (typically 1-3/4" or 2-3/4" between mounting holes) and different connector styles. Measure your old ignitor before ordering, or bring it to the HVAC supply house. The second most common mistake is touching the element, which is already covered. The third is assuming the ignitor is the problem without testing — replacing a $25 part when the real issue is a $200 control board is an expensive lesson.

DIY is genuinely not recommended in two cases: if your furnace uses a cracked heat exchanger as a symptom (carbon monoxide risk means you want a tech's eyes on the whole system), and if you're in an apartment where your lease or building code requires licensed work on gas appliances.

When Replacing the Ignitor Doesn't Fix It

About 70% of the time, a furnace that won't ignite and tests with an open-circuit ignitor will work perfectly after a new ignitor. The other 30% involves something the ignitor swap doesn't address. Here's what to check next if you've replaced the ignitor and the problem persists.

Flame sensor fouling

The flame sensor is a small metal rod that confirms the burner actually lit. If it's coated in residue — which happens over years of normal operation — it can't detect the flame reliably and will shut the gas valve within a second or two of ignition. The furnace appears to light briefly, then shuts down. Fix: lightly sand the sensor rod with fine steel wool or 600-grit emery cloth. This is a five-minute, zero-parts-cost fix and should be part of any annual maintenance. If cleaning doesn't work, replacement sensors run $10 to $30.

Gas valve failure

If the ignitor glows (you can see it through the sight glass or with the panel off — briefly, with caution) but gas doesn't flow, the gas valve may have failed. Gas valves cost $75 to $200 for the part; total repair with a tech runs $200 to $400. At that price point, factor in the age of your furnace — if it's over 15 years old, a full replacement conversation is worth having.

Control board failure

The control board manages the ignition sequence. A failed board may not send voltage to the ignitor at all, or may send it at the wrong time. Control boards for common residential furnaces run $80 to $250 for the part. A tech can test whether the board is outputting the correct voltage during the ignition sequence; you can too, with a multimeter, if you're comfortable working around live circuits during testing.

Pressure switch or inducer motor issues

If the draft inducer isn't creating enough negative pressure, the pressure switch won't close and the ignition sequence never starts. A failed pressure switch ($20 to $50 part) or a failing inducer motor ($150 to $400) can mimic an ignitor problem because the symptoms look identical from the outside: furnace starts, runs the motor, nothing ignites, lockout. The multimeter test on the ignitor will show it's fine — and that's your clue to look upstream.

The honest summary: if you've replaced a confirmed dead ignitor and the furnace still won't light, the next diagnostic step is checking whether the control board is actually sending voltage to the ignitor terminals during the startup sequence. Clip a multimeter set to AC voltage across those terminals when the furnace tries to start. You should see 80V to 120V for about 30 to 60 seconds. If you see nothing, the board is suspect. If you see correct voltage and the new ignitor still won't glow, you have a defective replacement part — rare, but it happens.

Is It Worth Repairing or Time to Replace the Whole Furnace?

A $150 to $300 ignitor repair is almost always worth doing on a furnace that is less than 15 years old and otherwise functioning. The math is clear: a new mid-efficiency furnace (80% AFUE) installed costs $2,500 to $4,500 depending on your market and equipment size; a high-efficiency 96% AFUE unit runs $4,000 to $7,000 installed. Spending $200 to avoid that cost makes obvious sense when the furnace has years of life left.

The calculus shifts when the furnace is old and other components are starting to fail. The heat exchanger is the critical one. A cracked heat exchanger leaks combustion gases — including carbon monoxide — into your living space. Replacement of a heat exchanger costs $500 to $1,500 in parts and labor, and most HVAC contractors will tell you honestly that on a furnace over 15 to 20 years old, that's a case for replacement rather than repair. If a tech mentions the heat exchanger while replacing your ignitor, take that seriously.

A useful rule of thumb from the HVAC trade: multiply the repair cost by the age of the furnace in years. If that number exceeds $5,000, lean toward replacement. So a $250 ignitor repair on a 10-year-old furnace scores 2,500 — repair. A $1,200 heat exchanger on a 20-year-old furnace scores 24,000 — replace. The rule isn't scientific, but it's a decent filter for borderline decisions.

One more factor: if your current furnace is 80% AFUE and you're in a climate with significant heating seasons, upgrading to 96% AFUE reduces gas consumption by roughly 16%. On a $1,500/year gas bill, that's about $240 per year in savings — meaning a new furnace pays back in 10 to 20 years on efficiency alone, before accounting for reliability. That's not a reason to replace a functional furnace, but it's context worth having when you're already facing a repair decision.