The furnace ignitor plays a crucial role in starting your gas furnace by lighting the burner. When ignition fails, a reset can clear temporary faults and restore operation in many situations. This guide explains what an ignitor does, when a reset is appropriate, and safe steps you can take. It also covers common post-reset issues and when professional service is needed, along with tips to prevent future problems.

What A Furnace Ignitor Does And The Main Types

The ignitor is a small, powered element that must heat to a high temperature quickly to ignite the gas burner. In modern furnaces, a hot surface igniter (HSI) made from silicon carbide or silicon nitride is common; it glows bright orange when energized and lights the gas when flames reach the burner. Older or hybrid systems may use an intermittent pilot with a thermocouple. A flame sensor on many models confirms that flame exists; if no flame is detected, the gas valve closes for safety. Ignitors are delicate components and can fail due to cracking, wiring fatigue, or overheating, which often triggers a fault code or a lockout in the furnace control board.

Typical types include:

Hot surface igniters (HSI) — ceramic or silicon-based elements that glow to ignite gas.
Intermittent pilot with thermocouple — older systems that keep a standing pilot flame while the thermostat calls for heat.
Flame sensor — a safety device that verifies flame presence and can prevent gas flow if the flame goes out.

Understanding your model helps determine whether a reset is appropriate and how the ignition sequence should behave after power restoration. If diagnostics show a fault code, consult the owner’s manual or a technician for model-specific guidance.

When Is It Appropriate To Reset The Ignitor

A reset is a practical first step when the furnace fails to ignite but shows no obvious mechanical damage. Typical indications include a blank or flashing status on the furnace’s LED, a brief glow from the ignitor followed by no flame, or a recent service event that triggered a lockout. A reset can clear transient electronic glitches or thermal lockouts that occur after a power surge, dirty filters, or short cycles.

Important safety note: do not repeatedly retry ignition if you smell gas or hear a hissing noise; this indicates a possible gas leak and requires immediate evacuation and professional assistance. If a reset does not restore ignition after a few attempts, or if you encounter persistent faults, schedule service to avoid carbon monoxide risks or furnace damage.

Safe Step-By-Step To Reset A Furnace Ignitor

Turn off power to the furnace at the service switch or main circuit breaker, and set the thermostat to an OFF position. Wait at least 60 seconds to allow residual voltages to dissipate.
Switch the thermostat back to HEAT and set it to a typical temperature; if your unit has a reset switch, locate the red or green reset button on the furnace cabinet or control panel and press and hold it for 3–5 seconds. If there is no reset button, proceed to the next step.
Power the furnace back on and observe the ignition sequence. Return to HEAT on the thermostat and listen for the ignition cycle. A healthy cycle usually includes the ignitor glowing and the burner lighting within 5–10 seconds. If the burner lights, allow the furnace to reach normal operating temperature.
If the ignitor glows but the burner fails to light, do not continue aggressive retry attempts. Wait 3–5 minutes between retries (this cooldown helps protect the ignitor and gas valve). If ignition still fails after a couple of cycles, discontinue attempts and contact a professional.
Check the gas supply at the furnace disconnect valve and ensure it is fully open. If you detect a gas odor or suspect a leak, evacuate immediately and call emergency services. Never operate a furnace with a known gas leak.
After a successful reset and ignition, monitor for repeated failures. Short cycling, frequent resets, or unusual noises can indicate issues beyond a simple reset, such as dirty flame sensors, worn ignitors, or blower motor faults.

Diagnosing Common Post-Reset Issues

If the furnace lights inconsistently or fails to stay lit after a reset, several causes are worth inspecting. The goal is to distinguish a simple cleaning need from a component failure that requires replacement or professional service.

Cracked or worn ignitor — visible damage or an irregular glow can indicate the ignitor needs replacement. A failing ignitor often glows dimly or takes too long to heat.
Dirty flame sensor — a dirty sensor can fail to detect flame, causing a lockout. Cleaning with a soft abrasive (gentle steel wool or fine emery cloth) after power is off can restore function; avoid bending the sensor and ensure it is clean and properly positioned.
Gas valve or pressure issues — if the gas valve sticks or gas pressure is low, ignition will fail. A pro can test gas pressure and valve operation safely.
Wiring and control board faults — loose connections, damaged wires, or a faulty control module can interrupt ignition sequencing. Inspect visible wiring for wear and have a technician test the control board signals.
Ventilation or combustion air problems — restricted venting or insufficient air supply can cause ignition failures or CO risk. Ensure vents are clear and air intake paths are unobstructed.
Clogged burners or dirty heat exchanger — soot and debris reduce combustion efficiency and ignition reliability. A professional cleaning may be required.

In all cases, refer to the furnace’s error codes and LED indicators. These codes guide diagnosis and indicate whether the fault is related to ignition, flame sensing, gas supply, or control electronics. If any step reveals a potential hazard, discontinue troubleshooting and call a licensed HVAC technician.

When To Call A Professional

Call a professional if ignition problems persist after a safe reset, if there are gas odors, or if you notice signs of long-running flame instability. A licensed technician can perform a gas valve safety check, flame sensor calibration, ignitor replacement, or control-board diagnostics with specialized tools. Ongoing issues can indicate hidden hazards such as gas leaks, improper venting, or faulty safety switches that require regulatory compliance and testing.

Professional service is especially important if the furnace is older, if you have a complex multi-stage system, or if you are unsure about any step in the reset process. Addressing ignitor faults promptly reduces energy waste, extends equipment life, and maintains indoor air safety.

Maintenance Tips To Prevent Ignitor Problems

Regular filter changes — dirty filters reduce airflow and force the furnace to work harder, increasing ignition stress. Replace filters every 1–3 months based on usage and indoor air quality.
Annual professional inspection — a yearly tune-up helps catch wear on ignitors, flame sensors, and burners before failures occur.
Keep ignition area clean — dust buildup on the ignitor and surrounding components can impede operation. Gentle cleaning during service visits helps maintain performance.
Check venting and combustion air — ensure exhaust paths are unobstructed and that the furnace has adequate fresh air supply to prevent incomplete combustion and ignition problems.
Inspect wiring and connections — loose or corroded connections can cause intermittent ignition. Ask a pro to tighten and test wiring integrity during service.
Replace aging ignitors — many hot surface ignitors last 5–10 years, depending on usage. Plan for timely replacement to avoid sudden outages.
Thermostat compatibility — ensure the thermostat is functioning correctly and communicating with the furnace. A faulty thermostat can mimic ignition issues by delaying or interrupting heat calls.

By following these maintenance steps, homeowners can reduce the frequency of ignition-related failures and improve overall furnace reliability. Remember that safety remains paramount; when in doubt, consult an HVAC professional rather than attempting risky repairs yourself.