When a furnace won’t light at all — the draft inducer runs, nothing glows, no flame — the hot-surface igniter is the first component to check. It’s the single most common furnace repair, and the fix is usually a $20–50 part that any mechanically confident homeowner can swap in 30 minutes.
Unlike a flame sensor (which causes light-then-shutoff symptoms), a failed igniter means the gas never lights in the first place.
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What the hot-surface igniter does
The hot-surface igniter is a ceramic heating element that glows hot enough to ignite natural gas or propane when the gas valve opens. It replaced pilot lights in most furnaces built after the mid-1980s. When the thermostat calls for heat:
- The control board starts the draft inducer (the fan that creates airflow through the heat exchanger).
- After a pressure-switch confirmation that airflow is established, the board energizes the igniter.
- The igniter heats up over 15–30 seconds (SiC) or 5–17 seconds (SiN) until it reaches ignition temperature.
- The gas valve opens; the igniter ignites the gas.
- The flame sensor confirms combustion; the igniter de-energizes and the burner runs normally.
A failed igniter breaks step 2–3: the element either doesn’t glow at all, or glows but at insufficient temperature to ignite the gas.
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Two types of igniters: silicon carbide vs. silicon nitride
Silicon carbide (SiC)
- Orange-red glow when energized
- More fragile — SiC is ceramic and cracks easily from physical impact or thermal shock (rapid heating from a cold start)
- Common in furnaces built before ~2005; still found in many Lennox and some Carrier units
- Cold resistance: typically 40–90 ohms (check your model’s manual)
- Fails by cracking — visually broken or burned through
Silicon nitride (SiN)
- Bright white/yellow glow when energized
- More durable than SiC; less prone to thermal-shock cracking
- Standard in most furnaces post-2005 (Goodman, Trane, Rheem, newer Carrier and Lennox)
- Cold resistance: typically 10–20 ohms (varies — confirm with your model)
- Fails by burning out internally — may look intact but won’t heat
How to identify your type: look at the igniter during a firing cycle through the sight glass on the furnace door panel. Orange glow = SiC. White/bright yellow = SiN. If the furnace is locked out, you can visually inspect the element by removing the door panel (with power off) — SiC igniters often show visible cracks when they fail.
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Symptoms of a failed furnace igniter
Furnace doesn’t ignite — no glow visible through sight glass. The clearest symptom. During a call for heat, the draft inducer runs normally, but you see nothing glowing through the small window on the door panel.
Furnace attempts ignition 3 times then locks out. The control board gives the igniter 3 chances. Without ignition confirmation from the flame sensor, it locks out. The LED on the control board will typically show a lockout code (Goodman 1-flash, Carrier code 14, varies by brand).
Furnace ignites intermittently — works sometimes, not others. A marginal igniter may heat enough to ignite gas in warmer conditions but fail in a cold basement or after the furnace has been off all night. This is a common failure pattern for aging SiC igniters with hairline cracks — the crack opens when the element is cold and may close slightly when warm.
Igniter glows but no flame appears. If the igniter heats but gas doesn’t ignite, the issue may be the gas valve, gas supply pressure, or (on some setups) the igniter not reaching full temperature due to low voltage. Don’t assume the igniter is the cause if you can confirm it’s glowing bright.
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How to visually inspect the igniter
You need: flashlight, power off, lower access panel removed.
- Turn off the furnace power switch.
- Remove the lower access panel.
- Locate the igniter — it’s inside the burner assembly, typically L-shaped or horseshoe-shaped, positioned near the first burner tube. It connects to the control board via 2 wires and a plug.
- Inspect the element visually:
– SiC igniter: look for cracks, chips, or a burned-through spot in the ceramic. A crack as thin as a hair is enough to cause failure — hold it up to a flashlight. – SiN igniter: harder to diagnose visually; the element may appear intact even when failed. Testing with a multimeter is more reliable.
Handle the igniter by its wire connector or ceramic base only. Do not touch the heating element with bare fingers — skin oils cause thermal hot spots that will shorten the new igniter’s life.
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Testing the igniter with a multimeter
A resistance (ohms) reading tells you whether the element is electrically intact — but note: a reading in range does not guarantee the igniter heats to ignition temperature under load. An igniter can have acceptable resistance and still fail to light gas. If symptoms point to the igniter and the resistance is at the high end of or above spec, replace it.
- Turn off the furnace power switch.
- Unplug the igniter connector from the wiring harness.
- Set your multimeter to resistance (ohms).
- Touch the probes to the two terminals in the igniter plug.
- Read the resistance:
| Igniter type | Expected range (cold) | Out of range |
|---|---|---|
| Silicon carbide (SiC) | 40–90 ohms | < 20 ohms (shorted) or open (∞) = failed |
| Silicon nitride (SiN) | 10–20 ohms (typical) | Open (∞) = definitely failed; confirm range with your model’s manual |
An open reading (no continuity, displays OL or ∞) means the element is broken internally — replace it regardless of visual appearance.
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Replacing the igniter
Parts: source the replacement igniter by your furnace model number (on the label inside the door panel or on the side of the unit). OEM igniter prices run $30–80. Universal replacement igniters (Emerson/White-Rodgers 767A-357 and similar) fit many furnaces at $15–25 and perform identically — confirm the resistance spec, mounting hole pattern, and connector match.
Tools needed: 1/4-inch nut driver or small socket set, needle-nose pliers (for connector), multimeter (optional).
Steps:
- Turn off furnace power at the wall switch or power toggle on the unit. Confirm the display is off.
- Remove the lower access panel.
- Unplug the igniter wiring connector — it’s usually a 2-pin Molex-style connector. Pull straight off; don’t yank the wires.
- Remove the mounting screws. Most igniters use one or two 1/4-inch hex screws. Support the igniter with one hand while removing the last screw — they’re fragile.
- Note the igniter orientation before removing. Most have a specific position relative to the burner — a photo is worth taking before removal.
- Install the new igniter. Handle by the connector or base only. Position per your photo. Finger-tighten the screws first, then snug them — don’t overtighten into the ceramic mounting block.
- Reconnect the wiring connector.
- Restore power and test. Call for heat. Watch through the sight glass — you should see the igniter glow within 15–30 seconds (SiC) or faster (SiN), followed by burner ignition.
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Cost comparison
| Approach | Part | Labor | Total |
|---|---|---|---|
| DIY (OEM igniter) | $30–80 | — | $30–80 |
| DIY (universal igniter) | $15–25 | — | $15–25 |
| HVAC service call | $30–80 | $120–220 | $150–300 |
The igniter is one of the most cost-effective DIY HVAC repairs. The main risk is physical fragility — SiC igniters crack if dropped or bumped. Take your time and handle carefully.
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When to stop and call a pro
- Igniter replacement doesn’t fix it: the control board may not be sending voltage to the igniter, or there’s a gas supply issue (pressure, gas valve, or gas service to the house).
- Gas smell during diagnosis: turn off gas supply, ventilate, call your gas company or HVAC tech. A gas smell is not an igniter problem.
- You can confirm voltage at the igniter terminals but no glow: low line voltage to the furnace, or a control board that’s not sending the 120V trigger to the igniter — both require further diagnosis.
- Inducer motor doesn’t start: without the inducer, the board won’t energize the igniter. The inducer is upstream in the sequence — fix that first.
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FAQ
How do I know if the igniter is getting power? With a multimeter set to 120V AC, carefully probe the igniter terminals (power ON, furnace calling for heat, during the ignition warm-up period). You should see ~120V AC during the warm-up phase. No voltage = the board isn’t sending the signal — could be a pressure switch, control board, or wiring issue, not the igniter itself.
Will a failed igniter trigger a flash code? Yes — after 3 failed ignition attempts, the control board logs a lockout or ignition-failure code. On Goodman that’s 1-flash; on Carrier it’s typically code 14; codes vary by brand. See your brand’s flash-code guide.
Can I use a universal igniter instead of OEM? Usually yes, but confirm three things: (1) resistance spec is in the same range as your OEM igniter, (2) the mounting hole pattern matches, (3) the connector type matches or an adapter is included. Universal igniters from Emerson/White-Rodgers are widely trusted; cheap no-name igniters have inconsistent quality.
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Related guides
- Furnace Not Heating: Diagnostic Order — if igniter replacement doesn’t resolve no-heat, continue with the full ladder (gas supply, pressure switch, flame sensor, control board)
- Furnace Flame Sensor: Symptoms and Cleaning — if the igniter glows but the burner shuts off after 5–10 seconds, the flame sensor is the next suspect
- Carrier Furnace Fault Codes · Goodman Furnace Flash Codes — the fault code on your board (e.g., Code 14 on Carrier, 1-flash lockout on Goodman) confirms the igniter sequence is failing
The old igniter looks fine — no visible cracks. Should I still replace it? If symptoms match (no ignition, correct flash code) and the multimeter shows open or very high resistance, yes — SiN igniters often fail internally with no visible damage. If resistance is in spec and you can visually confirm no glow during a firing attempt, the board may not be delivering voltage to the igniter.
How long does a hot-surface igniter last? SiC igniters: 3–7 years in average use; SiN igniters: 7–15 years. Both fail most commonly at startup from thermal shock, not from continuous operation. This is why intermittent cold-start failures are the typical failure pattern.
