As a homeowner, you must embrace the maintenance cycle if you want to have a functional home. This is essential because a home's infrastructure, including appliances and electronics, degrades over time. For example, with time, people's HVAC systems have deteriorated...
Faulty Gas Furnace Igniter
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Faulty Gas Furnace Igniter
A faulty furnace igniter normally begins with a furnace not starting up, no heat or inconsistent heat. This may or may not happen with visible damage to the igniter. It is useful to know before you have a complete failure and no heat in the Winter.
Some Signs Your Gas Furnace Igniter Is Failing
- Furnace Won’t Start or Struggles to Ignite. If your thermostat calls for heat but the furnace doesn’t fire up, the igniter may not be heating enough to light the burners.
- Furnace is Blowing Cold Air, A furnace that runs but only pushes cold air often indicates the burners never ignited—commonly due to a weak or dead igniter.
- Frequent On‑and‑Off Cycling called Short cycling can occur when the igniter intermittently fails to light the burners, causing the system to shut down and retry.
- Clicking or No Glow From the Igniter. Modern igniters typically glow bright orange.
If you hear clicking with no glow—or the glow is faint—the igniter may be cracked or burned out. - Visible Cracks or Damage Igniters endure extreme heat (up to 1,800°F), making them prone to cracking over time. A visual inspection often reveals breaks or discoloration.
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Main Types of Gas Furnace Igniters
The four core igniter types used in residential gas furnaces are well‑established across HVAC industry sources.
- Hot Surface Igniter (HSI)
- Uses a silicon carbide or silicon nitride element that glows red‑hot to ignite gas.
- Very common in modern furnaces.
- Lifespan: 3–10 years depending on material and cycling frequency.
- Direct Spark Ignition (DSI)
- Produces a high‑voltage spark directly at the burner—similar to a gas stove spark.
- Eliminates the need for a pilot light.
- Lifespan: 10–20 years.
- Intermittent Pilot Ignition
- Uses a spark to light a small pilot flame only when heat is needed.
- More efficient than a standing pilot because the flame isn’t always on.
- Standing Pilot Ignition
- Traditional always‑on pilot flame.
- Rare in modern furnaces but still found in older systems and some appliances.
Some Reasons for a Failed Furnace Igniter
Some Reasons for a Failed Furnace Igniter
- Thermal stress from repeated heating cycles
- Dirt or debris buildup
- Electrical issues
- Age and wear
- Improper handling during maintenance (they’re fragile!)
A furnace ignitor can fail due to wear and tear from repeated heating cycles, dirt buildup, electrical issues, or corrosion. A faulty igniter may also result from a power surge or temperature fluctuations, preventing it from properly igniting the gas.
Any one of these issues can lead to a Furnace Igniter failing. If it does fail, it will need to be replaced by a licensed technician.
What to Do Next
If you suspect a bad igniter:
- Turn off power to the furnace before inspecting
- Avoid touching the igniter—even oils from your fingers can damage it
- Call a licensed HVAC technician for diagnosis and replacement
A faulty igniter is a common and relatively inexpensive repair, but it’s essential for safe furnace operation. Only a licensed HVAC technician should replace these sensitive, but essential parts.
Contact us at Air Doctor Heating and Air , All or Text Us at 301-799-7200
HVAC Licenses
- MD HVAC # 17747
- WV HVAC # 07874
- VA HVAC # 2710071510
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