In winter, when the temperatures drop, you expect your furnace to push out warm air without hesitation. You turn up the heat, the blower kicks on as it should, and then everything suddenly stops. The system pauses before the burners ever ignite, and the furnace shuts itself down without producing any heat. The furnace continues to malfunction despite several attempts, making your house uncomfortably cold. When the furnace ignitor is not working correctly or wears out, it prevents the burners from firing, causing the furnace to repeatedly attempt ignition before safely shutting down. These issues rarely appear overnight. They often begin with slow ignition, unusual clicking, or a furnace that runs longer than necessary to reach the set temperature.
This guide explains the reasons for this component’s failure and the early symptoms.
Why Is the Furnace Ignitor so Important?
The furnace ignitor may appear small, but it determines whether your home receives heat. When the thermostat signals for heat, the ignitor activates, and the heating element engages. It heats up, glows, and lights the gas burners. Without that spark, nothing else in the system can work.
Modern furnaces no longer use pilot lights. They rely on electronic ignitors because they’re safer, cleaner, and far more efficient.
A strong, healthy ignitor ensures:
- Fast, reliable burner ignition
- Stable heat throughout the home
- Lower energy waste
- Safe furnace operation
- Fewer startup furnace ignition failures and error codes
The same mechanical stresses that damage an ignitor can also cause a furnace gas valve to malfunction, so both parts should be checked together.
What Causes a Furnace Ignitor to Crack or Fail?
A furnace ignitor goes through more stress than most people realize. It sits in one of the hottest areas of the furnace and is exposed to extreme heat every time the system fires up, making it one of the most heavily stressed components of the ignition process. At that stage, many homeowners try simple bad ignitor troubleshooting, but the underlying cause is usually more complex.
Here’s what really causes an ignitor to crack or stop working:
1. Thermal Issues
The ignitor is forced to expand, cool, and contract during each heating cycle. This creates micro-cracks in the ceramic body. Over time, those tiny cracks grow until the ignitor breaks completely. This is the number one reason ignitors fail.
2. Dust and Dirt Buildup
A dirty ignitor takes longer to heat up. When it can’t reach the right temperature, the furnace won’t ignite. Dust also traps heat at the ignitor surface, accelerating wear and leading to early cracking.
3. Electrical Problems
Ignitors depend on a precise voltage range. Even slight voltage changes can burn out the element. Loose wiring, weak control boards, and aging electrical connectors all deliver unstable power, which damages the ignitor.
4. Moisture Exposure
Humidity and condensation can weaken the ceramic surface of the ignitor. Once moisture seeps in, the material loses strength and cracks faster during heating. Over time, repeated exposure creates tiny fractures that spread with every ignition cycle. In damp basements or poorly ventilated utility areas, this process accelerates, leading to early failure of the ignitor.
5. Mishandling During Installation
Ignitors are incredibly fragile. Touching them with bare hands, bumping them against metal, or overtightening screws can weaken the ceramic. Even a fingerprint can cause a hot spot, leading to early failure.
6. Poor Airflow or Blocked Filters
Restricted airflow inside the furnace causes temperatures to rise above usual. When the heat becomes uneven or excessive, the ignitor overheats. That extra stress shortens its lifespan and increases the chance of burnout.
How Do Different Ignitor Problems Affect Furnace Behaviour?
Various ignitor problems present in different ways. Each one has its own effect on the furnace, and learning those patterns not only helps prevent a complete system failure but also makes it easier to know when it’s time to schedule professional furnace repair services in San Marcos, TX.
Here’s a brief overview of the most common ignitor issues and how they affect a furnace’s operation.
| Ignitor Problem | What the Homeowner Notices | What’s Happening Inside the Furnace |
| Crack in the ignitor | The furnace tries to start but fails after a few seconds. | The ignitor heats unevenly. It can’t reach the required ignition temperature, so the control board shuts the system down for safety. |
| Ignitor glowing weakly or dim orange | Long delay before the heat starts; cold air blowing from vents at first. | Dirt, dust, or age prevents the ignitor from reaching full heat. Burners can’t ignite on time, causing slow or incomplete startup cycles. |
| Ignitor is not glowing at all | No heat throughout the home; repeated clicking noises. | The ignitor has burned out or lost electrical continuity. The control board keeps attempting ignition, but without a heating element, the gas cannot ignite. |
| Ignitor overheating or showing burn spots | The furnace starts sometimes but shuts off quickly, resulting in inconsistent heating. | The ignitor overheats due to airflow issues or aging. Excess stress creates hot spots, making ignition unreliable and triggering a safety lockout. |
| Ignitor damaged during installation or cleaning | The system fails soon after a recent service or part replacement | Accidental tapping, or improper mounting, can weaken the ceramic surface, leading to early cracks or electrical failure. |
| Incorrect voltage reaching the ignitor | Intermittent heat; furnace may work some days and fail on others | The control board or wiring is supplying an unstable voltage. The ignitor receives either too little power to heat properly or too much, causing burnout. |
| Ignitor is misaligned with the burners | Burners light unevenly or sputter before fully igniting | The ignitor isn’t positioned correctly, so the gas doesn’t ignite at the right spot. This leads to delayed ignition and rough startup cycles. |
| Moisture exposure on the ignitor surface | The furnace hesitates before starting or shuts down mid-cycle. | Humidity or condensation disrupts the ignitor’s ability to heat up, causing inconsistent ignition and system interruptions. |
Final Thoughts!
An inoperable igniter can be hazardous. The moment homeowners notice cracked ignitor symptoms or experience repeated ignition delays and early-startup failures is the time to take action. By addressing the problem early, you can keep your furnace running, prevent a shutdown, and avoid cold nights.
When the issue appears, the safest move is to call a trusted HVAC partner. This is where Woods Comfort Systems, a leading HVAC and plumbing company, is the trusted choice. We bring decades of experience, deep knowledge of furnace systems, and a customer-first approach that Texas homeowners rely on year after year. Call today or book your appointment and get fast, expert service that restores heat, protects your home, and keeps your furnace running strong.
