Furnace Won't Ignite? Common Ignitor Problems Las Vegas Homeowners Face

Key Takeaways

• The hot surface ignitor is the most common reason a gas furnace won't light in Las Vegas — especially after months of summer dormancy.
• Las Vegas furnaces face a unique failure mode: thermal shock from sitting idle through 115°F summers then firing up on a 38°F October night.
• Symptoms include furnace clicking but not lighting, blower running with no heat, and repeated lockout cycles.
• Most ignitor replacements cost $150–$350 all-in and take less than an hour of professional labor.
• Check thermostat, breaker, and gas valve first — then read the error code blinking on the control board before calling a tech.
• Annual fall maintenance catches weak ignitors before they fail on the coldest night of the year.

October hits Las Vegas. It's been a long summer — 115-degree days, AC running non-stop for months, and your furnace sitting completely idle in the attic or garage since March. Then the temperature drops into the upper 30s one night — the kind of cold that surprises visitors who think Vegas is always hot — and you flip the thermostat over to heat for the first time in seven months.

Nothing happens.

Or maybe you hear clicking. Or the blower motor starts running and air moves through the vents, but it's cold air. You wait. You reset the thermostat. You try again. Still nothing. The house drops to 62°F by midnight and you're googling "furnace won't ignite Las Vegas" in a mild panic.

Here's what's almost certainly happening: your igniter has failed. It's the single most common reason a gas furnace won't light, and Las Vegas homes are particularly vulnerable because of the extreme thermal stress these components go through. Understanding why — and what to do about it — can save you a cold night and help you make a smart decision about repairs.

How furnace ignition works

Modern gas furnaces don't use matches. They rely on an ignition system that creates enough heat or spark to light the gas burners safely and reliably. There are three types you'll find in Las Vegas homes, depending on when the furnace was manufactured.

Hot surface ignitor vs. electronic spark vs. standing pilot

Hot surface ignitor (HSI) — This is what you'll find in virtually every furnace installed after the mid-1990s. It's a small, fragile element made from silicon carbide or silicon nitride that glows orange-hot (around 1,800–2,500°F) when electricity passes through it, igniting the gas as it flows past. Silicon carbide ignitors are older and more brittle; silicon nitride versions are more durable and increasingly common in furnaces made after 2010. If you have a furnace that's 5–25 years old, it almost certainly has an HSI.

Electronic spark ignition — Less common in residential furnaces, but you'll find it in some makes. Instead of glowing, it produces a series of rapid electrical sparks (think: the clicking sound on a gas stovetop). These are generally more reliable than HSI systems but still fail with age.

Standing pilot light — Older furnaces (pre-1990s) used a continuously burning pilot flame. If you have a furnace this old, the pilot can blow out or the thermocouple that monitors it can fail. This is becoming rare in the Las Vegas market, but plenty of older homes in established neighborhoods like Whitney Ranch or downtown Vegas still have them. If your furnace is this vintage, we need to have a different conversation about heating replacement — but that's for later.

The ignition sequence, step by step

When your thermostat calls for heat, a specific sequence unfolds inside the furnace:

1. The control board receives the heat call and checks that all safety circuits are closed.
2. The inducer motor starts, pulling air through the heat exchanger to purge any residual gas.
3. The pressure switch confirms that the inducer is working and the flue is drafting properly.
4. After a brief purge period (typically 15–30 seconds), the ignitor energizes. On an HSI system, it begins glowing.
5. Once the ignitor reaches operating temperature, the gas valve opens, releasing gas to the burners.
6. The gas ignites. The flame sensor confirms combustion within a few seconds.
7. The ignition module signals the control board that the flame is proven.
8. The blower motor starts, pushing heated air through the ducts into your home.

If any step fails, the whole sequence stops. The control board logs an error code and — after usually three attempts — enters safety lockout. That's why you might hear clicking and then silence, or watch the whole thing try and fail multiple times before giving up.

Why Las Vegas furnaces fail at ignition

Ignitors fail everywhere, but they fail more often — and fail in a particular way — in Las Vegas. The desert environment creates conditions that don't exist in most of the country.

Thermal shock: the Vegas-specific failure mode

This is the big one. Hot surface ignitors are essentially ceramic heating elements, and ceramics don't love rapid temperature changes. In most climates, a furnace might sit dormant for 3-4 months. In Las Vegas, your furnace sits completely unused from roughly March through October — sometimes longer. That's 6-7 months of just sitting in a garage or attic where summer temperatures can hit 130°F or more in the enclosed space.

Then November arrives with a cold front. The overnight low drops to 35°F. You turn on the heat. The ignitor, which has been baking in an attic all summer, now has electricity surging through it and is being asked to glow to 2,000°F within seconds. That's an extreme thermal event for a fragile ceramic component that's already a few years old.

Silicon carbide ignitors are especially vulnerable. They develop micro-cracks over time — sometimes invisible to the naked eye — that widen just enough under thermal stress to create a break in the circuit. The ignitor won't glow, the gas won't light, and you're cold. This is why so many Las Vegas furnace repair calls happen on the first cold night of the season rather than mid-winter. It's not bad luck. It's physics.

Attic furnace installations are particularly exposed to this. Many Las Vegas homes — especially those built in the 1990s and 2000s in communities like Summerlin, Green Valley, and Henderson — have their furnaces installed horizontally in the attic. Unlike a basement furnace in Chicago that stays relatively climate-controlled year-round, an attic furnace in Vegas bakes all summer. By October, every heat-sensitive component in it has been through a punishment that most HVAC equipment was never designed to handle.

Desert dust and spider webs in burner assemblies

Las Vegas has some of the finest particulate dust of any major city in the country. Haboobs roll through the valley, coating everything with a thin film of alkaline Mojave dust. During the months your furnace sits idle, this dust settles on the burner ports, the flame sensor, and the ignitor itself.

A layer of dust on a hot surface ignitor doesn't prevent it from glowing — but it can create hotspots that accelerate cracking. More critically, dust and debris on the burner ports can create delayed ignition: the gas flows, the ignitor glows, but the burner doesn't light immediately because the ports are partially blocked. Then the gas builds up slightly and ignites with a small bang. This rollout is hard on the ignitor and can cause the high limit switch to trip.

And then there are the spiders. This sounds strange, but HVAC technicians throughout the Southwest will tell you: spiders love dormant furnace burner assemblies. They're dry, enclosed, and protected. After seven months of disuse, it's not uncommon to find webs in and around the burner assembly that can disrupt gas flow and ignition. This is another reason why a fall maintenance visit before the first cold snap matters so much in Vegas.

An annual check from our heating maintenance team catches exactly these kinds of issues — before they leave you without heat on a 38°F night.

Age and normal wear

Even without the Vegas-specific stressors, ignitors have a finite lifespan. Silicon carbide ignitors typically last 3-7 years. Silicon nitride ignitors are rated for around 7-10 years. If your furnace is 8-12 years old and has never had the ignitor replaced, it's living on borrowed time — especially given the desert climate.

Age matters in another way too: as ignitors wear, they don't always fail completely at first. They start drawing less current, which means they glow at a lower temperature. The gas may still light — sometimes — but the startup becomes unreliable. You might get heat on a mild night when everything cooperates, but fail on a colder night when the ignitor needs to work harder. This intermittent failure pattern is particularly frustrating and easy to misdiagnose.

Symptoms of a failing ignitor

Knowing what to look for before you call a technician helps you describe the problem accurately and confirms you're not dealing with something simpler like a thermostat issue or tripped breaker.

The furnace clicks but doesn't light

If you have an electronic spark system, you'll hear rapid clicking when the furnace tries to ignite. If that clicking happens but no flame follows — and the furnace shuts down after a few attempts — that's a textbook ignition failure. On an HSI system, there may be no audible sign that anything is happening at all, since the ignitor glows silently.

The blower runs but only cold air comes out

This confuses a lot of homeowners. The forced air system is delivering air through your vents, so something is working — but it's cold. What's happening is that the furnace went through its sequence, failed to prove a flame, locked out on ignition, but the blower either continued running or came on as programmed. The burners never lit. The air moving through your ducts is just ambient temperature. This scenario almost always points to either the ignitor or the flame sensor — a technician can tell the difference quickly with a simple current draw test on the ignitor.

The furnace tries multiple times then goes quiet

Most furnace control boards are programmed to attempt ignition 2-3 times before entering safety lockout. You might notice the system cycling: the inducer starts, there's a pause, it tries again, another pause, tries one more time — then silence. After lockout, the furnace won't try again until the board is reset (usually by cycling the thermostat off and back to heat, or cutting power at the breaker). If it just keeps doing the same thing every time you reset it, the underlying ignition problem hasn't gone away.

Intermittent operation — works sometimes, fails other times

This is the signature of a marginal ignitor that hasn't fully failed yet. On a mild 50°F night, it barely manages to get hot enough to light the gas. On a 35°F night, when it needs to work a little harder, it can't quite make it. If your furnace has been unreliable — working fine some days and failing on others — don't wait for it to fail completely. A weak ignitor won't heal itself, and full failure tends to happen at the worst possible time.

Burning smell at startup

A mild dusty smell when the furnace first fires up for the season is normal — that's accumulated dust burning off the heat exchanger. But if you smell something more acrid, like burning plastic or an electrical smell, that could indicate the ignitor is failing in a way that's stressing other components. Don't ignore it. A heat exchanger crack or wiring issue can produce similar smells and is considerably more serious.

Error codes and what they mean

Most furnaces made after 2000 have an LED on the control board that blinks error codes. This is your furnace telling you exactly what went wrong — and it's remarkably useful if you know how to read it.

Find the small viewing window on the lower access panel of your furnace (it's usually on the front face, about the size of a quarter). Look for a blinking LED and count the flashes. The code chart is almost always printed on a sticker inside the access panel door itself.

Common codes related to ignition failure:

• 3 flashes — On most furnace brands (Carrier, Bryant, Lennox, Rheem, Trane), 3 flashes indicates an ignition failure or pressure switch problem. This is the most common code for ignitor issues.
• 4 flashes — Often indicates a high limit switch trip, which can be caused by restricted airflow or a faulty ignitor that caused delayed ignition and heat rollout.
• 6 flashes — Frequently means the control board sensed voltage at the ignitor circuit but failed to prove a flame — another ignition-related code.
• Continuous flashing or no light at all — Could indicate a board failure, blown fuse, or complete power loss to the control circuit.

These codes vary by manufacturer, so always check the sticker on your specific furnace. But if you're seeing 3 flashes and your furnace won't light, you've got very strong evidence that ignition is the problem. Take a photo of the code chart and the LED, then share it with your technician — it'll speed up the diagnostic significantly.

What to check before calling a tech

Before you schedule a service call, run through these checks. Some of them will reveal a problem that isn't the ignitor at all — and that's useful information either way.

Thermostat settings

This sounds obvious, but you'd be surprised how many no-heat calls trace back to a thermostat that was left in "Cool" mode or set below the current room temperature. Make sure:

• The system is set to "Heat" (not "Cool" or "Off")
• The setpoint is several degrees above the current room temperature
• The fan is set to "Auto" rather than "On"
• Thermostat batteries aren't dead (a weak battery can cause erratic behavior)
• No vacation hold or eco mode is blocking the heat call

If you recently installed a smart thermostat or changed any settings, that's worth revisiting. A thermostat that's wired incorrectly — particularly if the common wire (C-wire) is missing or connected to the wrong terminal — can cause all kinds of strange furnace behavior that looks like an ignition problem but isn't.

Circuit breaker and furnace power switch

Check the breaker panel for a tripped breaker labeled "Furnace" or "HVAC." A tripped breaker won't be fully in the "On" position — it'll be slightly in between. Flip it fully off, then back on. Also look for a light-switch-style power switch near the furnace itself, typically mounted on the wall or on the unit. It's easy to accidentally switch this off, especially in garage furnace installations where it might get bumped during the months the furnace isn't being used.

Also confirm the blower compartment door is fully closed and latched. There's a safety switch inside the cabinet that cuts power if the door is even slightly ajar. It's a surprisingly common culprit after a filter change.

Gas supply

Make sure the gas control valve on the gas line serving the furnace is open (the handle should be parallel to the pipe, not perpendicular). If you've had any recent gas work done on the house or used your gas range and water heater normally, gas supply to the furnace is probably fine. But if nothing gas-powered in your home is working, call Southwest Gas before calling your HVAC company.

Also check: did you recently run your gas fireplace or outdoor grill for the first time in months? There can be a brief period where air in an unused gas line causes delayed lighting. This is a minor issue that resolves itself, not a furnace problem.

Filter condition

A severely clogged filter won't prevent the ignitor from working, but it can cause the high limit switch to trip after ignition — because the heat exchanger overheats when airflow is restricted. Pull the filter out and hold it up to light. If you can't see light through it, replace it. This is one of the most overlooked causes of heating failures and costs about $10 to fix. See our full furnace maintenance checklist for filter change guidance specific to the Vegas dust environment.

The error code on the control board

As described above — locate the viewing window on the furnace access panel, count the blinks, and find the code chart on the door sticker. Document what you see. If you can share a photo or describe "3 flashes, pauses, then 3 more flashes" to your technician, you've already done half their diagnostic work.

What NOT to do

Don't repeatedly reset the furnace trying to force it to light. Most boards allow 3 ignition attempts before lockout for a reason — repeated failed attempts push unburned gas into the system, and stressing an already-failing ignitor isn't going to fix it. One reset to confirm the failure pattern is reasonable. After that, call for service.

Don't touch the ignitor with your bare hands. If a technician needs to inspect or replace it, the oils from skin contact can create hotspots that shorten the new ignitor's life. This is a job for gloves and proper tools.

Our broader furnace troubleshooting guide covers additional scenarios — including what to do when the furnace starts but doesn't stay on, and how to handle strange sounds and smells at startup.

Ignitor replacement cost in Las Vegas

Ignitor replacement is one of the more affordable furnace repairs — which is good news, because it's also one of the more common ones. Here's what to expect:

Parts cost

The ignitor itself typically costs $20–$80 depending on the furnace brand and model. OEM (original equipment manufacturer) parts from brands like Lennox, Carrier, or Rheem run on the higher end. Universal aftermarket ignitors compatible with most brands are available for less. Your technician may have a preference based on reliability history — silicon nitride aftermarket ignitors have a good track record when sourced from reputable suppliers.

Labor cost

Ignitor replacement is fast — usually 20–40 minutes of actual work once the technician is on site. Labor in the Las Vegas market typically runs $80–$130 per hour for standard service hours. The diagnostic fee is usually $75–$150 and is often credited toward the repair if you approve the work.

All-in cost

Expect to pay $150–$350 total for ignitor replacement during normal service hours. If you're calling on a weekend evening or during a cold snap when every HVAC company in town is busy, after-hours emergency rates can add $75–$200 to that total.

For context: this is considerably less than a control board ($300–$700 installed), blower motor ($400–$800 installed), or flame sensor ($100–$250). If a technician is recommending ignitor replacement after a proper diagnostic, it's usually worth doing even on an older furnace — as long as the unit doesn't have more serious underlying issues. Our detailed furnace repair cost guide for Las Vegas breaks down prices for all common repairs if you want to compare.

Flame sensor cleaning vs. replacement — the common confusion

The flame sensor is often confused with the ignitor because they both affect whether the burner stays lit. The flame sensor is a thin metal rod that sits in the flame path and confirms combustion. When it gets coated with oxidation (which happens quickly in the desert environment), it can fail to detect the flame and signal the board to shut off the gas — even when the ignitor worked fine and the flame lit successfully.

Flame sensor cleaning is much less expensive than ignitor replacement: usually $75–$150 as a standalone service. Replacement of a failed sensor runs $100–$250. If your technician says both the ignitor and flame sensor need attention, that's not unusual — they're both worn-out ignition components that often fail around the same time, especially on furnaces that have been running through several Las Vegas seasons without maintenance.

Check our HVAC pricing guide for current estimates on all furnace-related repairs.

Typical ignitor lifespan in Las Vegas

Industry standard lifespan for a silicon carbide ignitor is 3–7 years. Silicon nitride: 7–10 years. But in Las Vegas, given the thermal stress from summer attic temperatures and the shock of first startup, plan for the lower end of those ranges. If your furnace is over 8 years old and has the original ignitor, that component is a fair candidate for proactive replacement during a fall maintenance visit — before it fails on a cold night in late October.

Repair or replace the whole furnace?

A failed ignitor alone is not a reason to replace your furnace. It's a relatively minor repair, and if the rest of the system is in good shape, replacing the ignitor and getting several more years of service from the furnace is a perfectly sound decision.

The calculus changes in a few situations:

Multiple failures in a single season

If you've replaced the ignitor once and now the flame sensor is going, and last year it was the control board, you're seeing a pattern of systemic component failure. At some point, the accumulated repair costs tell you something about where the furnace is in its lifecycle. The industry rule of thumb: if a single repair exceeds 40-50% of the cost of a new system, replacement is worth serious consideration. For a system that's had multiple repairs in recent years, the math changes even faster.

Age and efficiency

Most gas furnaces have a useful lifespan of 15–20 years. Older units typically have AFUE ratings of 80% or lower — meaning 20 cents of every dollar of gas is going up the flue. Modern high-efficiency furnaces run at 96% AFUE. In a mild-winter climate like Las Vegas, the payback on that efficiency upgrade is slower than in a cold-weather city — but if your furnace is 18 years old, failing ignitors, and the heat exchanger needs inspection, replacement may be the smarter long-term move anyway.

Our repair vs. replace guide walks through the full decision framework if you're on the fence. And if you're looking at replacement, our furnace replacement cost guide for Las Vegas covers what to expect from new system pricing. You can also explore gas furnace vs. heat pump options — heat pumps have become increasingly viable in the desert climate and may qualify for federal efficiency incentives.

What replacement looks like

If you are looking at a new system, The Cooling Company handles the full process — from sizing and selection to furnace installation in Las Vegas and post-installation tune-up. We're also a furnace replacement resource if you're still figuring out which direction to go.

How to prevent ignitor failure

You can't prevent all ignitor failures — they're wear items that eventually reach end of life — but you can dramatically reduce the chances of being left without heat on a cold night through a few habits specific to the Las Vegas climate.

Schedule a fall tune-up before October

This is the single most effective thing a Las Vegas homeowner can do. A proper fall heating maintenance visit includes an ignitor current draw test — the technician uses an amp meter to measure how much current the ignitor is drawing when energized. A healthy silicon carbide ignitor typically draws 3–4 amps. As it ages and develops micro-cracks, that number drops. A reading below 2.5 amps usually signals a marginal ignitor that's close to failure. Catching it during a maintenance visit costs far less than an emergency repair on a Saturday night in November.

The same visit also cleans the flame sensor, clears debris from the burner assembly, checks the gas control valve, and verifies that the heat exchanger is intact — the full system review that ensures the first cold night goes smoothly. Learn more about our heating maintenance services in Las Vegas.

Change the filter regularly

Vegas dust is aggressive. A filter that might last 90 days in Seattle can fill up in 30-45 days in the Mojave. A clogged filter doesn't directly cause ignitor failure, but the restricted airflow it creates stresses the heat exchanger and can cause limit switch trips that create abnormal thermal cycling — which adds wear to ignition components. During heating season (typically November through March in Vegas), check the filter monthly.

Protect the attic furnace from summer extremes

If your furnace is in the attic, make sure the attic is adequately ventilated to reduce peak temperatures. A properly ventilated attic in Vegas might peak at 120–130°F in summer vs. 140–150°F in a poorly ventilated one. That temperature difference matters for every heat-sensitive component in the system, including the ignitor, control board, and capacitors. If your attic insulation is inadequate, addressing that has multiple benefits — including extending furnace component life.

Don't skip the first-season startup test

A week before you expect to need heat for the first time — usually late September or early October in Las Vegas — run the furnace for a test cycle on a mild evening. If it fails to light, you've got time to schedule a non-emergency repair appointment rather than calling at 10 PM on the coldest night of the year. It costs nothing and gives you an early warning if something is marginal.

The complete furnace maintenance checklist covers every step of this fall startup process in detail.

Consider a service plan

For homeowners who want consistent coverage and priority scheduling during the fall rush, a preventive maintenance plan makes sense. It keeps your furnace inspected annually, builds a service history, and typically includes discounts on parts and repairs when something does need attention. Talk to our team about what's available for your system.

Decision guide: when to call vs. when to wait

Call immediately if:

• You smell gas near the furnace — leave the house and call from outside
• A CO detector has alarmed, even briefly
• You see scorch marks, smoke, or sparks around the furnace
• The furnace has been in lockout repeatedly and won't stay running after resets

Schedule service within 24-48 hours if:

• The furnace clicks or tries to ignite but won't light
• The blower runs but no warm air reaches the vents
• The furnace lights intermittently and you've confirmed thermostat/filter/power are fine
• The control board shows a 3-flash or similar ignition error code

This can probably wait for a maintenance appointment if:

• The furnace is running fine now but hasn't been serviced in over a year
• You're seeing the first mild 55°F days and want a pre-season check before it gets cold
• The furnace is over 8 years old and has never had the ignitor inspected

What a furnace ignitor replacement service looks like

So you've confirmed the ignitor is the likely culprit and you've called for service. Here's what the visit typically looks like:

The technician arrives, starts with a system diagnostic, and tests the ignitor using an amp meter or visual inspection through the viewing window. On an HSI furnace, they'll verify whether the ignitor glows when energized — and how brightly. If it doesn't glow at all, or glows dimly at clearly insufficient temperature, replacement is confirmed.

They'll turn off the gas and electrical supply to the furnace, remove the access panels, and carefully extract the old ignitor — which mounts on a bracket near the burner assembly. The new ignitor is seated, wired, and tested. The technician will cycle the furnace through a complete startup to confirm it lights reliably and that the flame sensor proves the flame properly.

A thorough tech won't stop there. They'll also check the heat exchanger for cracks, clean the flame sensor while they're in there, verify gas pressure, test the high limit switch, and confirm the blower is moving adequate air across the exchanger. If you're paying for a service call, the whole system should get a look — not just the failed part.

The total time on-site is usually 1–1.5 hours. Total cost: $150–$350 depending on the ignitor part and whether any additional components need attention.

Local context: when furnace breakdown season hits Las Vegas

If you're calling us in late October or November, you're almost certainly not alone. This is the period Las Vegas HVAC companies call "furnace breakdown season" — the weeks after the first hard cold snap when furnaces that have been idle all summer reveal their weaknesses all at once.

During peak breakdown season, response times stretch and emergency rates apply more often. The best way to avoid this is to schedule your fall furnace check in September, before the rush. But if you're reading this at midnight on a cold November night with a 40°F forecast and a furnace that won't light — call us. We serve Summerlin, Henderson, North Las Vegas, Spring Valley, and all the surrounding areas, and we understand the urgency of being without heat in a house that was designed primarily for cooling.

The Las Vegas valley is full of single-story stucco homes that lose heat fast. The temperature drop from 70°F at sunset to 38°F by 3 AM happens quickly in the desert, and those walls don't hold heat the way a wood-frame home in a milder climate does. A furnace failure in Vegas is genuinely uncomfortable and occasionally dangerous for vulnerable household members. Don't tough it out waiting for business hours if you have elderly residents or young children. Our Las Vegas furnace repair team can help.

For a broader look at all the heating services we provide — from maintenance to full replacement — visit our heating hub. And if you're comparing your options between repair and a new system, our furnace replacement page or the repair vs. replace decision guide is a good starting point. You can also explore furnace installation options if your current system is reaching the end of its viable life.

External resources worth bookmarking: the U.S. Department of Energy's furnace efficiency guide, the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) for equipment standards and certified product listings, and the Energy Star furnace ratings database if you're evaluating replacement options.

Need HVAC Service in Las Vegas?

The Cooling Company provides expert HVAC service throughout Las Vegas, Henderson, and North Las Vegas. Our licensed technicians deliver honest assessments, upfront pricing, and reliable results.

Call (702) 567-0707 or visit furnace repair, heating maintenance, AC repair, or installation for details.

Why homeowners trust The Cooling Company

• Serving Las Vegas since 2011 with 55+ years combined experience
• Licensed, EPA-certified technicians and safety-first inspections
• BBB A+ rated with a 100% satisfaction guarantee
• Lennox Premier Dealer with local parts support

Neighborhoods we serve for furnace repair

• Summerlin, The Lakes, and Queensridge
• Henderson, Green Valley, and Anthem
• North Las Vegas, Aliante, and Centennial Hills
• Spring Valley, Paradise, and Winchester
• Downtown Las Vegas, Rancho, and Arts District

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