Furnace Ignitor Not Glowing: Causes, Troubleshooting, and Fixes for Homeowners

When your furnace ignitor is not glowing, your heating system cannot ignite and will fail to warm your home. This common issue frustrates many American homeowners, especially during the cold months. Identifying the root causes and solutions is key to restoring comfort and efficiency. Below, discover why a furnace ignitor may stop glowing, how to diagnose the problem, and what steps you can take to fix it.

Common Reasons Why A Furnace Ignitor Is Not Glowing

A furnace ignitor relies on heat to light the gas and start the heating process. When it fails, several underlying issues may be at play. The following are the most frequent causes:

• Faulty Ignitor: The ignitor may be cracked, broken, or burned out.
• Electrical Issues: Problems with wiring, power supply, or circuit boards can prevent operation.
• Safety Switches: A tripped flame sensor, limit switch, or pressure switch may cut power to the ignitor.
• Gas Flow Interruptions: Gas valve issues or supply problems can affect ignitor function.
• Control Board Malfunction: A faulty furnace control board may fail to send voltage to the ignitor.
• Thermostat Failures: Incorrect thermostat command or connection can prevent ignition attempts.

How A Furnace Ignitor Works

Modern gas furnaces often use a hot surface ignitor, which glows red hot and ignites the gas when the furnace cycle begins. Here’s the basic sequence:

1. The thermostat signals for heat.
2. The furnace control board begins a startup sequence that powers the ignitor.
3. The ignitor heats to high temperatures (often above 2,000°F).
4. Once the ignitor glows, the gas valve opens, allowing gas to ignite.
5. The furnace warms the home until the thermostat resets.

A failure in this sequence—especially when the ignitor is not glowing—stalls the entire process and leaves your furnace cold.

Signs Your Furnace Ignitor Has Failed

Recognizing the symptoms of a failed ignitor can help with speedy repairs:

• No Heat: The furnace cycles, but no warm air is produced.
• No Glow: When peeking into the burner compartment, the ignitor remains dark.
• Frequent Cycling: The furnace starts and stops repeatedly without igniting.
• Clicking Sounds: Several ignitors make a faint click or snap when attempting to light.
• Error Codes: Newer furnaces may flash a diagnostic code related to ignition problems.

Safety Precautions Before Troubleshooting

Always prioritize safety when dealing with gas appliances and electrical components. Before inspecting or repairing a furnace:

• Turn off electrical power at the furnace switch or breaker box.
• Shut off the gas supply using the dedicated gas valve.
• Allow components to cool completely before touching internal parts.
• Consult the user manual, and wear gloves and safety glasses.

If you’re unsure or uncomfortable, or if you smell gas, immediately call a licensed HVAC technician for professional assistance.

Step-By-Step Troubleshooting For A Furnace Ignitor That’s Not Glowing

Diagnosing why your furnace ignitor is not glowing is a matter of systematic checks. Use the following steps as a guideline:

1. Check The Thermostat Settings

Confirm that the thermostat is set to “heat” and programmed above the current room temperature. Replace batteries or touch panel if unresponsive.

2. Inspect Furnace Power Supply

Ensure the power switch (often located next to the furnace) is in the ON position. Check for tripped circuit breakers or blown fuses.

3. Look For Error Codes

Modern furnaces have LED indicators that flash codes. Open the access panel and match any flashes with the diagnostic key on the furnace label.

4. Remove The Furnace Panel And Check The Ignitor

Locate the ignitor, usually shaped as a ceramic rod with electrical connections. Look for visible cracks, chips, or white residue which signal damage.

5. Test The Ignitor For Continuity

Use a multimeter set to the ohms (Ω) scale. Unplug the ignitor and place probes on each terminal. A healthy ignitor usually reads 40-200Ω. No reading or OL means it’s faulty.

6. Inspect Safety Switches

The limit switch, pressure switch, or flame roll-out switch could cut 120V power to the ignitor. Test each switch for continuity, or observe if one has been tripped.

7. Check Furnace Control Board

Visually inspect for burned, corroded, or broken solder joints. If the board does not send 120V to the ignitor at startup, it may require replacement.

8. Assess Gas Valve And Gas Flow

Gas supply issues prevent ignition. Inspect the manual valve and confirm it’s open. If you suspect a gas valve fault, call a professional HVAC technician.

How To Replace A Broken Furnace Ignitor

Replacing a furnace ignitor is a simple DIY task if you’re comfortable with basic tools and safety precautions. Here’s how:

1. Power off the furnace at the breaker and switch.
2. Remove the access panel to locate the ignitor assembly.
3. Disconnect the wire harness or unplug the ignitor leads.
4. Unscrew or unclip the ignitor from its bracket. Do not touch the ceramic tip with bare hands; use gloves.
5. Install a new, compatible ignitor in reverse order. Securely connect wiring and mount hardware.
6. Restore power and run a heating cycle to verify operation.

Replacement ignitors usually cost between $25 and $75. Always match the ignitor type and model to your furnace’s specifications.

Additional Causes For Furnace Ignitor Not Glowing

Beyond a failed ignitor itself, several system issues can cause the ignitor not to glow:

• Loose Or Damaged Wiring: Vibration or corrosion can break connections to the ignitor or control board.
• Poor Grounding: Lack of proper ground can prevent ignition voltage from reaching the ignitor.
• Excessive Moisture: Water can damage ceramic and electrical components.
• Dirty Components: Accumulated dust can reduce conductivity and trap heat.
• Incorrect Ignitor Installed: Using a non-matching or off-brand ignitor can prevent proper startup.

How To Prevent Furnace Ignitor Problems

Regular furnace maintenance minimizes the chances of a failed ignitor:

• Change furnace filters every 1-3 months to reduce dust buildup.
• Schedule annual inspections by a certified HVAC professional.
• Keep the furnace area clean and clear of debris or stored objects.
• Monitor for odd sounds or startup delays and address them quickly.

Maintenance costs are minor compared to emergency repairs or loss of heat during cold spells.

When To Call An HVAC Professional

For many homeowners, basic troubleshooting is safe and manageable. However, call a certified technician if you encounter:

• Repeated ignitor failures within short time spans.
• Unusual gas odors near the furnace area.
• Visible electrical arcing, burn marks, or melted wires.
• Error codes you cannot reset or decipher.
• Any uncertainty about your ability to complete a repair.

Professional diagnosis prevents further damage and ensures safe operation.

Furnace Ignitor Overview: Hot Surface Vs Intermittent Pilot

Most homes use one of two ignitor types:

Ignitor Type	Description	Common Problems
Hot Surface Ignitor (HSI)	Ceramic element glows red to ignite gas directly.	Cracking, burnout, electrical failure, wrong replacement part.
Intermittent Pilot Ignitor	Sparks to light a small pilot flame, which in turn lights the burners.	Electrode wear, safety switch faults, dirty pilot assembly.

Identify your ignitor type for accurate troubleshooting and replacement.

Frequent Mistakes To Avoid With Furnace Ignitors

• Touching new ignitor tips with bare hands (oil from skin causes premature failure).
• Forgetting to turn off power and gas before repairs.
• Installing mismatched ignitor models.
• Ignoring manufacturer replacement procedures.
• Forcing ignitor connections, causing damage to terminals.

How Long Should A Furnace Ignitor Last?

With proper care, a furnace ignitor should last 4-7 years. Factors such as cycling frequency, local water quality, household dust, and heating demand can influence longevity. If your furnace frequently “short cycles,” this shortens the ignitor’s lifespan.

Energy Efficiency Implications Of A Failed Ignitor

A non-glowing ignitor means your heating system cannot light, making energy use inefficient or causing safety shutdowns. Timely repair ensures energy dollars are not wasted and heating is restored quickly.

How To Read Furnace Error Codes Related To Ignition

Most new furnaces flash codes when ignition fails:

• Locate the blinking LED light behind the lower furnace panel.
• Count the number of flashes—it repeats in patterns.
• Check the sticker or diagram on the panel to decode the error (e.g., “three flashes = pressure switch failure”).
• Reset system after addressing the issue to clear the code.

This helps pinpoint ignitor or related circuit failures.

Costs Of Ignitor Replacement And Professional Repair

Homeowners report average costs of $150–$350 for professional ignitor replacement, including the part and labor. DIY replacement parts alone usually cost $25–$75.

Complex issues involving sensors or circuit boards can run $400 or more, depending on your furnace model and regional labor rates.

Where To Buy Furnace Ignitors

Furnace ignitors are widely available at:

• HVAC supply stores and local hardware chains.
• Major online retailers (Amazon, Home Depot, Lowe’s).
• Order by furnace brand and specific model number for guaranteed fit.

Save all packaging for return in case of part mismatch.

FAQs: Common Questions About Furnace Ignitor Not Glowing

• Can I run my furnace if the ignitor isn’t glowing?
  No, the furnace cannot ignite gas without a functioning ignitor.
• How do I know if my ignitor is bad or another part is failing?
  Multimeter testing of the ignitor is the best first step; if power is present and the ignitor remains dark, it’s likely failed.
• Will replacing the ignitor fix my furnace problem?
  Often yes, but not if another system component is also faulty (control board, switches, gas valve).
• Can a dirty air filter keep the ignitor from glowing?
  It’s rare, but a clogged filter may trigger safety switches that indirectly shut down ignition.

Summary Table: Troubleshooting Steps For Furnace Ignitor Not Glowing

Troubleshooting Step	What To Check	Action
Thermostat	Correct mode and temperature	Reprogram or replace batteries
Power Supply	Breaker, switch, fuses	Restore or replace as needed
Ignitor	Visual damage, continuity	Replace if faulty
Safety Switches	Continuity, proper reset	Replace or reset
Control Board	Power output to ignitor	Replace if defective
Gas Valve	Flow and operation	Call HVAC technician

If your furnace ignitor is not glowing, using these insights can save time, money, and stress—restoring warmth and comfort to your home.