Furnace Ignitor Types and How to Know When Yours Is Failing

If your furnace isn't starting — no flame, no heat, just a blower that eventually shuts off — there's a good chance the ignitor is the culprit. The ignitor is the component that lights the gas in your burner, and it's one of the most common furnace repair items. Here's everything Minnesota homeowners need to know.

The Two Types of Furnace Ignitors

1. Standing Pilot Light (Older Furnaces, Pre-1990s)

Older gas furnaces use a standing pilot — a small continuous flame that stays lit 24/7 and ignites the main burner when heat is called for. The pilot is kept lit by a thermocouple, a safety device that senses the pilot flame and keeps the gas valve open.

Signs of pilot problems:

• Pilot flame goes out repeatedly
• Yellow or orange pilot flame (should be blue)
• No heat despite thermostat calling for it

Common fix: Relight the pilot per the label on your furnace. If it won't stay lit, the thermocouple likely needs replacement ($10–$35 DIY, $75–$150 service call).

Note: If you have a standing pilot furnace, it's likely 25+ years old. An 80% AFUE at best, possibly 65–70% if truly old. The efficiency argument for replacement is very strong.

2. Hot Surface Ignitor (HSI) — All Modern Furnaces

Every furnace built since roughly 1990 uses a hot surface ignitor (HSI) instead of a standing pilot. The HSI is a small, fragile component — typically made of silicon carbide or silicon nitride — that glows red-hot (1,800°F+) for a few seconds when your thermostat calls for heat. This ignites the gas in the burner assembly.

HSIs are more energy-efficient than pilot lights (no continuous gas burn) but are fragile — they can crack from vibration, age, or even oil from bare hands during installation.

Hot Surface Ignitor Materials: Silicon Carbide vs. Silicon Nitride

Most Goodman furnaces from 2010 onward use silicon nitride ignitors, which are significantly more durable than the older silicon carbide style.

Signs Your Hot Surface Ignitor Is Failing

The HSI fails in two ways: it either cracks and won't heat up, or it weakens and no longer gets hot enough to reliably light the burner. Signs to watch for:

• Furnace clicks on, blower starts, then shuts off with no heat — classic HSI failure sequence
• Intermittent heat — starts fine sometimes, fails other times (especially on cold mornings)
• Error code on your furnace board — most modern furnaces flash an LED error code; 3 blinks often indicates ignition failure (check your manual)
• Furnace age 7–10+ years with no ignitor replacement — silicon carbide ignitors have a limited life expectancy

Diagnosing an Ignitor Failure

If you're comfortable with basic DIY and want to confirm an ignitor failure before calling a tech:

1. Turn off power to the furnace at the breaker or disconnect switch
2. Locate the ignitor — it's typically near the burner assembly, visible through an access panel
3. Visually inspect for cracks (use a flashlight — even a hairline crack means failure)
4. Use a multimeter on resistance (ohms) setting: a good silicon carbide ignitor reads 40–90 ohms; silicon nitride reads differently by model. Check your furnace documentation or the Goodman/Daikin tech resources for your specific model number
5. If the ignitor shows infinite resistance (no continuity), it's failed

Replacing an Ignitor: DIY or Service Call?

HSI replacement is one of the more accessible DIY furnace repairs:

• Part cost: $15–$60 depending on type and model
• Service call cost: $150–$350 including labor
• Skill level: Low — typically 2 screws and a plug connector. The only caution: never touch the ignitor surface with bare hands — skin oil causes hot spots that crack the ceramic. Use gloves or handle by the wires/bracket only.

Make sure to get the right replacement: use your furnace's model number (found on the label inside the front panel door) to look up the correct ignitor part number. Universal ignitor kits are available but confirm compatibility with your specific furnace.

When an Ignitor Repair Doesn't Solve the Problem

If you've replaced the ignitor and the furnace still won't start, the problem may be:

• Flame sensor failure — furnace lights but immediately shuts off (1–3 seconds of flame)
• Control board failure — board not sending voltage to ignitor at all
• Gas valve failure — ignitor glows but no gas flow
• Pressure switch or inducer failure — furnace won't attempt ignition sequence at all

If your furnace is 15+ years old and needs a control board or gas valve ($200–$600 in parts), that's the point where a new factory-direct furnace often makes more financial sense.

Shop New Goodman Furnaces — Factory Direct →