Your furnace clicks. Then clicks again. Then nothing. No heat, no comfort, just cold air coming through the vents while the temperature outside keeps dropping.
Sound familiar? You might be dealing with a bad furnace ignitor, and catching it early could save you from a full system lockout in the middle of winter.
At Quality Heating, Cooling, Plumbing & Electric, we see this problem a lot, especially during cold snaps across Tulsa, Broken Arrow, Owasso, and the surrounding communities. The good news? A failing ignitor usually gives you warning signs before it quits entirely. The better news? Knowing what to look and listen for can help you act fast.
Here’s what to watch for, and what to do about it.
What Does a Furnace Ignitor Actually Do?
Before getting into the symptoms, it helps to understand what this part does.
Modern gas furnaces don’t use a standing pilot light anymore. Instead, they use a hot surface ignitor (HSI) that heats up rapidly, reaching temperatures high enough to ignite the gas burners safely. Think of it like a glowing filament. When it works, combustion happens and heat flows. When it doesn’t, the whole cycle breaks down.
The ignitor is small but critical. And because it goes through rapid heating and cooling every time your furnace runs, it wears down over time.
6 Signs Your Furnace Ignitor May Be Failing
These are the symptoms homeowners most commonly notice before a full breakdown. You don’t need to open anything or touch any wiring. These are all observable from your thermostat, vents, and ears.
1. Repeated Clicking With No Heat
Your furnace tries to start, clicks 2 or 3 times, then goes quiet. No warmth follows.
This is one of the most common signs. When the ignitor can’t reach the temperature needed to light the gas, the system attempts ignition a few times and then locks out as a safety measure.
What you’ll notice: Clicking sounds from the unit, followed by silence or the blower running without any warm air.
2. Cold or Barely Warm Air From Your Vents
Your blower is running. Air is coming out. But it’s cold.
If combustion never starts because the ignitor failed, the blower still pushes air through the system. That air just isn’t heated. Homeowners frequently search “why is my furnace blowing cold air” when this happens, and a failed ignitor is often the culprit.
3. Delayed Ignition or a Noticeably Longer Warm-Up
You set the thermostat, walk away, and come back 20 minutes later to a still-cold room.
A weakening ignitor may still function but take much longer than usual to heat up enough to light the burners. This intermittent behavior often gets worse over time.
4. Frequent Short Cycling (On-Off-On-Off)
The furnace turns on, runs briefly, turns off, then starts again in a short loop without ever reaching temperature.
Each failed ignition attempt is a cycle. If your furnace is cycling more than usual without heating your home, this pattern is worth taking seriously before it leads to a full lockout.
5. Intermittent or Inconsistent Heating
Some rooms are warm, others aren’t. Or the heat works fine some days and barely functions on others.
Gradual ignitor wear often shows up as inconsistency first. The part still works, but not reliably. Over weeks or months, it becomes more frequent until the ignitor fails completely.
6. Higher Energy Bills With Less Comfortable Heat
When your furnace works harder and longer to heat your home without success, energy use climbs. If your utility bill went up but your home feels colder, your system may be struggling at the ignition stage.
Gradual Wear vs. Sudden Failure: What’s the Difference?
Not every ignitor failure looks the same.
Gradual wear is more common. Repeated heating and cooling cycles slowly degrade the element. You’ll see symptoms like delayed starts, intermittent failures, and progressively worse performance over weeks or months. This gives you time to act.
Sudden failure can happen from a cracked element, power surge, or physical damage. One day the furnace works fine; the next, nothing. No warming-up period, just immediate no-ignition.
Either way, the fix is the same: professional diagnosis and replacement if confirmed bad.
Why You Can’t Always Tell by Looking at It
This is important, and a lot of homeowners are surprised by it.
Visual inspection is not a reliable way to confirm ignitor failure.
Micro-cracks, internal degradation, and contamination often don’t show up to the naked eye. An ignitor can look perfectly fine and still fail completely when powered.
As one HVAC technician put it in an active Reddit HVAC community discussion:
“The only way to know they are bad is to ohm it out. They look fine visually.”
This is why technicians use a multimeter to measure resistance (with power off and wires disconnected). A functioning hot surface ignitor shows measurable resistance at room temperature. An infinite resistance reading (“OL” on a multimeter) confirms failure.
Resistance Ranges Technicians Look For
Here’s a reference table based on manufacturer data from CoorsTek, Trane, and HVAC training resources (2023–2025):
| Ignitor Type | Typical Room-Temperature Resistance | Notes |
| Silicon Carbide (e.g., Norton 201) | 40–90 ohms (up to 400 in some models) | Higher values can signal wear |
| Silicon Nitride (e.g., CoorsTek, Glowfly) | 40–80 ohms or 65–120 ohms (some as low as 11–17 ohms) | Varies by model; check OEM specs |
| White-Rodgers / Norton variants | 40–75 ohms or model-specific | Silicon nitride versions often test lower |
Source: CoorsTek Igniter Specifications, Trane HSI Troubleshooting and Specifications, HVAC training materials (2023–2025)
A reading outside these ranges, or an “OL” (open line/infinity) reading, confirms the ignitor needs to be replaced. This is not something we recommend homeowners test themselves. Gas and electrical systems require licensed professionals for safe handling.
If you’re unsure whether your system is showing ignitor issues, our team at Quality Heating, Cooling, Plumbing & Electric is ready to help. Contact us for professional furnace repair services before a failing ignitor turns into a full system lockout.
How Long Should a Furnace Ignitor Last?
Average lifespan falls between 3 and 7 years, though some ignitors last up to 10 years under favorable conditions.
Factors that shorten ignitor life include:
- Frequent on/off cycling
- Dirty or clogged air filters restricting airflow
- Dust buildup on the ignitor itself
- Voltage fluctuations or power surges
- Physical handling (oils from skin can create hot spots that damage the element)
Silicon nitride ignitors generally outlast older silicon carbide models due to their greater durability.
If your furnace is over 10 years old and showing any of the symptoms above, it’s worth having the full system evaluated, not just the ignitor.
Ignitor vs. Flame Sensor: Don’t Confuse the Two
These are two separate parts, and they cause similar symptoms but at different points in the startup cycle.
| Furnace Ignitor | Flame Sensor | |
| When it acts | Before gas ignites | After gas ignites |
| What it does | Heats up to light the burners | Detects that a flame is present |
| Failure symptom | No ignition at all | Flame starts but quickly shuts off |
| How it’s tested | Resistance (ohmmeter) | Microamp current reading |
If your furnace lights briefly and then shuts off after a few seconds, the flame sensor is more likely the issue than the ignitor. Both require professional diagnosis and should not be handled by homeowners without proper training.
Symptom Checklist: What Your Furnace Is Telling You
| Symptom | Likely Ignitor Related If… | Other Possible Cause | What to Do |
| Repeated clicking, no heat | Ignitor fails to glow | Control board, gas valve | Call a technician |
| Starts then shuts off quickly | No sustained ignition | Flame sensor, limit switch | Do not keep resetting; call for service |
| Cold air from vents | No combustion occurring | Blower issue, thermostat | Schedule a service call |
| Delayed or intermittent heat | Element weakening | Dirty burners, low gas pressure | Inspect before lockout occurs |
| Furnace over 10 years old with symptoms | Age-related wear | Overall efficiency decline | Full system evaluation recommended |
When to Call Quality Heating, Cooling, Plumbing & Electric
Here’s a simple way to think about it: if your furnace isn’t heating your home and you’ve noticed any of the signs above, it’s time to call.
Resetting your system repeatedly without identifying the cause can lead to:
- System lockout (where the furnace won’t attempt startup at all)
- Damage to the control board
- Gas-related safety risks if ignition keeps failing
A licensed technician from Quality Heating, Cooling, Plumbing & Electric will check the full picture: error codes, ignitor resistance, gas pressure, flame sensor, and safety switch status. That complete picture tells us exactly what’s going on, not just a guess.
We serve homeowners across Tulsa, Bartlesville, Bixby, Broken Arrow, Catoosa, Claremore, Collinsville, Glenpool, Jenks, Muskogee, Owasso, Sand Springs, Sapulpa, Wagoner, and dozens of other communities across northeast Oklahoma.
How to Reduce the Risk of Ignitor Failure
You can’t prevent all wear, but you can slow it down.
Change your air filter every 1 to 3 months. Restricted airflow causes the furnace to overheat, which puts extra stress on components including the ignitor.
Schedule an annual furnace tune-up. ACCA maintenance standards (ANSI/ACCA 4 QM-2019) include inspection of the hot surface ignitor for cracks or white spots when energized, along with resistance testing and voltage checks. Catching a weakening ignitor during a tune-up is far better than dealing with a breakdown at midnight in January.
Consider a surge protector for your HVAC system. Power fluctuations can crack ignitor elements or shorten their lifespan significantly.
Don’t touch the ignitor surface. If a technician or previous owner has handled the ignitor without gloves, oils from skin contact can create uneven hot spots that accelerate failure.
Don’t Wait Until You’re Left in the Cold
A furnace ignitor rarely fails without sending signals first. The repeated clicking, the cold air, the furnace that starts and stops without ever heating the room. These aren’t random quirks. They’re your system telling you something is off.
At Quality Heating, Cooling, Plumbing & Electric, we’ve helped homeowners across Tulsa and northeast Oklahoma get ahead of furnace problems before they become emergencies. Whether it’s a quick ignitor check during a tune-up or a full diagnosis when the heat stops working, we’re here to make it straightforward.
If your furnace is showing any of these signs, contact Quality Heating, Cooling, Plumbing & Electric today for professional furnace repair services and honest answers about what your system needs.
Frequently Asked Questions
What are the most common signs of a bad furnace ignitor? The most common signs include repeated clicking sounds during startup without the burners lighting, the furnace blowing cold air, the system starting and shutting off quickly, delayed heating, and frequent short cycling. These symptoms are documented across multiple HVAC resources updated through early 2026.
Can I test my furnace ignitor myself? Visual inspection alone is unreliable. Professionals use a multimeter to check resistance values (typically 40–90 ohms for silicon carbide ignitors at room temperature). Testing involves disconnecting electrical wiring and working near gas components, which carries real safety risks. We strongly recommend contacting a licensed technician rather than attempting this yourself.
How long does a furnace ignitor last? Most ignitors last between 3 and 7 years, with some lasting up to 10 years depending on how often the furnace runs, filter maintenance, and other factors. Silicon nitride ignitors generally outlast older silicon carbide types.
What’s the difference between a bad ignitor and a bad flame sensor? The ignitor is responsible for starting combustion. The flame sensor confirms combustion is happening. If your furnace won’t ignite at all, the ignitor is more likely the issue. If it lights briefly then shuts off, the flame sensor is a more likely cause. A professional can confirm which part is failing through a complete diagnosis.
Is a bad furnace ignitor dangerous? A failing ignitor itself isn’t immediately dangerous, but repeated failed ignition attempts can lead to system lockout or, in some cases, unburned gas buildup if the gas valve stays open too long during failed starts. This is another reason not to keep manually resetting the system without getting it checked by a qualified technician.
How much does furnace ignitor replacement cost? Pricing varies based on the ignitor model, system brand, and service provider. We don’t list fixed prices here since costs change and differ by situation. Contact Quality Heating, Cooling, Plumbing & Electric for an honest assessment and accurate quote for your specific system.
Does furnace ignitor failure happen more in winter? Yes. Furnaces run more frequently during cold months, which accelerates ignitor wear. Real-time reports from January and February 2026, including from the Tulsa area, confirm that ignitor-related service calls spike during winter cold snaps.
Can a furnace ignitor be cleaned instead of replaced? In some cases, a technician may clean a slightly contaminated ignitor. However, once an ignitor’s resistance falls outside manufacturer specifications or it shows physical damage, replacement is the correct fix.
