If your furnace won’t ignite, the issue often traces back to the ignitor. It’s the tiny part responsible for kicking on your heat. When it goes bad, your whole house feels it. No warmth. No noise. Just cold air and a significant other muttering, “Should’ve called Lee Company,” under their breath.

A quick furnace ignitor test can save you hours of guessing (and hundreds on unnecessary repairs). In this guide, you’ll learn what your ignitor does, why it fails, how to test it safely, and when to bring in a professional.

We’ve been keeping the Southeast warm since 1944. If things go sideways, we’ve got your back.

What a Furnace Ignitor Does and Why It Fails

A furnace ignitor is the component responsible for lighting the gas that heats your home. No spark from the ignitor? No combustion.

No combustion? No heat. It’s one of the most essential parts in the whole system and also one of the most common to wear out.

When you turn up the thermostat, your furnace starts its ignition sequence. The ignitor heats up, glowing orange-hot like a toaster coil, and triggers the flame in the combustion chamber. That flame then heats the air that circulates through your home. Without the ignitor, the whole process stalls.

Gas furnaces last 15 to 30 years, with the average around 20 years with regular maintenance, but the ignitor inside? It’ll likely need replacing long before that. Here’s why:

• Normal Wear and Tear: The ignitor heats up and cools down over and over again. Eventually, all that cycling takes its toll, and the part just gives out.
• Carbon Buildup or Dirt: Dust and debris can block the ignitor or dull its glow just enough to keep it from sparking ignition.
• Electrical Issues: Loose wires, low voltage, or power surges can interrupt the ignition signal.
• Cracked or Burned-Out Surface: A crack in the ceramic surface means the ignitor is toast. No need to test here. Just replace it.
• Moisture Damage: Rust or corrosion from nearby water sources (like a leaky water heater) can short the ignitor or kill its heat.

How to Tell if a Furnace Ignitor Is Bad

When homeowners call us because their heat suddenly stops working, we always start with the ignitor. It’s one of the most common failure points in gas furnaces, and one of the easiest to diagnose if you know what to check.

Here’s how we pinpoint a bad ignitor (and how you can too).

Clicking, But No Ignition

You hear your furnace click like it’s trying to start … but nothing happens. That sound is the ignitor trying (and failing) to light the gas. If it keeps clicking with no flame, that’s strike one.

No Glow from Ignitor

During startup, a healthy ignitor glows bright orange before ignition. If yours stays dark, it’s either fried or not getting power.

Cracks or Chips

Carefully remove the panel and inspect the ignitor’s surface. Cracks or burn marks mean it’s time to replace the furnace ignitor.

Use a Multimeter

Want to be sure? A multimeter test is the gold standard. Set it to measure continuity. If the ignitor shows no continuity, it’s done for. If it does, the issue might lie elsewhere.

Check for Voltage

No voltage means no ignition. If your ignitor has power but won’t glow, the ignitor’s bad. However, if there’s no voltage at all, it might be the control board or wiring.

Not 100% sure what you’re looking at? That’s what we’re here for.

One quick call to us, and we’ll take it from there.

How to Test a Furnace Ignitor

To test your furnace ignitor safely, follow these step-by-step instructions below. This process will help you confirm if the ignitor is the culprit or if something else is blocking your heat.

We can’t emphasize this enough: Don’t rush it.

One wrong move with live wires or gas lines, and you’ll have a much bigger problem than a cold living room.

Turn Off Power and Gas

Safety first. Head to your breaker panel and shut off the power to the furnace. Then turn off the gas supply at the shutoff valve near your unit. You don’t want electricity or fuel running while your hands are inside the system. Double-check both are OFF before continuing.

Remove the Access Panel

Take off the furnace’s front panel to access the internal components. You’ll find the ignitor mounted near the burners (usually a flat, dark gray piece with wires leading to it).

If you’re not sure what you’re looking at, take a quick photo and look up your furnace model online for reference.

Visually Inspect the Ignitor

Before you even grab a tool, give it the eyeball test. Look for:

• Cracks or chips in the ceramic
• Soot, carbon buildup, or corrosion
• Discoloration or burn marks

Any of those? Time to replace the furnace ignitor. No further testing needed.

Use a Multimeter to Test Continuity

Here’s the official furnace ignitor test:

1. Set your multimeter to measure ohms (Ω).
2. Detach the ignitor’s wires from the circuit.
3. Touch one probe to each terminal.

If the screen shows infinity (or OL), your ignitor is dead. If it shows resistance (usually between 40-90 ohms), it’s working.

Replace the Ignitor If Needed

Found a problem? Replace it with the exact model number and specs. Cheap universal ignitors may not work with your furnace and can fail fast. Stick with OEM parts to avoid repeat problems.

Restore Power and Gas, Then Test the Furnace

Put the access panel back on, turn the gas and power back on, and set your thermostat to heat.

You should see the ignitor glow within 30 seconds, followed by the gas flame.

If that glow never shows up (or you’d rather not play amateur electrician), our licensed electricians have done this thousands of times. Let us handle it!

How to Prevent Furnace Ignitor Failure This Winter

To prevent furnace ignitor failure this winter, you need to keep your system clean, dry, and professionally maintained. Regular tune-ups and small maintenance tasks go a long way in preventing cold-night breakdowns, expensive emergency calls, and family members giving you that look when the heat goes out.

Older furnaces already operate at just 56-70% efficiency. A bad ignitor can make things worse by burning more gas, straining your system, and shortening the furnace’s lifespan. Fortunately, a few small habits can keep your ignitor alive and well all season long.

Here’s what we recommend to our customers every fall:

• Schedule a seasonal furnace tune-up: A licensed HVAC technician can catch a failing ignitor before it stops working entirely.
• Replace your air filter every 1-3 months: Dirty filters restrict airflow. This causes your furnace to overwork, which wears out the ignitor faster.
• Keep the area around your furnace clean and dry: Clutter traps moisture, and moisture leads to corrosion, which kills ignitors.
• Never touch the ignitor surface with your bare hands: Oil from your skin can cause hotspots and early failure.

We can handle all of the above. And if you’re a Lee Company+ member, your seasonal HVAC inspections are already included. That’s one less thing to worry about!

What Not to Do When You Test a Furnace Ignitor

Knowing how to test a furnace ignitor is only half the battle. Just as important is knowing what not to do.  Rushing the process, using the wrong tools, or skipping safety steps can lead to expensive damage or even serious injury.

Every year, we get calls from homeowners who tried to fix it themselves and ended up with a cracked ignitor, a fried control board, or a furnace that still doesn’t work. If you’re going to attempt this, slow down, stay safe, and avoid these common mistakes.

Forgetting to Turn Off Power and Gas

This one’s non-negotiable. Skipping this step is flat-out dangerous. Always cut power at the breaker and shut off the gas valve before opening up your furnace. No exceptions.

Handling the Ignitor Too Roughly

The ignitor’s ceramic surface is fragile. Bump it, tap it, or twist it too hard, and it cracks. Then you’ve got a bigger problem than just a furnace that won’t ignite.

Using the Wrong Replacement Part

Every furnace ignitor has specific voltage, shape, and resistance requirements. A generic replacement might not work. Or worse, it might fail fast and fry your control board.

Blaming the Ignitor Without Testing

Not all ignition issues mean the ignitor’s bad. Sometimes it’s the flame sensor. Sometimes it’s the control board. That’s why proper furnace ignitor troubleshooting matters.

When to Call a Professional HVAC Contractor to Replace a Furnace Ignitor

If you’ve tested the ignitor and the furnace still won’t ignite, it’s time to call a licensed HVAC professional. At this point, you’re beyond a simple DIY fix, and continuing to tinker could do more harm than good.

Here are the signs you’re in over your head:

• The multimeter shows continuity, but there’s still no ignition. That means the issue is deeper (likely the flame sensor, circuit board, or a gas flow problem).
• You already replaced the ignitor, but nothing changed. Don’t burn through parts hoping one will work.
• You smell gas. Stop everything and get out of the house.
• Other electrical components are unresponsive. This points to a control board issue, not the ignitor.
• You’re unsure. Trust your gut. If you’re second-guessing what you’re doing, call us.

DIY can save you money … until it doesn’t. Don’t risk gas leaks, electrical damage, or voiding your warranty. Let us take it from here.

Need a Local HVAC Company for Furnace Ignitor Replacement?

Testing your furnace ignitor is a smart move. However, if you’ve swapped the part, flipped the breakers, checked the voltage, and still can’t get the heat on, it’s time to tap in a professional.

Our licensed, insured HVAC technicians have been doing this since 1944. We’ve helped thousands of homeowners across Tennessee, Kentucky, Alabama, and Georgia avoid mid-winter meltdowns (literally and emotionally!).

And if you’re a Lee Company+ member, you’re already ahead of the game. You get four seasonal system checks a year, priority service, no emergency fees, and coverage for your home’s heating, air conditioning, plumbing, and electrical, so the little stuff doesn’t become big-dollar chaos.

Need a full furnace replacement? We’ve got financing ready to go!

Request an appointment today to keep your home’s heating in check.