Why Does My Furnace Pilot Light Go Out? (Factors & Fixes)

Why Does My Furnace Pilot Light Go Out? (Factors & Fixes)
Roger Bakies
Residential Sales Professional

I have been in the residential/light commercial HVAC business for 30 years. I grew up in a sheet metal fabrication shop and have installed, serviced, sold and helped people choose new systems to best fit their needs and lifestyle. I look forward to helping you pick the best fit for your home!

About This Article

If your furnace has a pilot light, chances are you’re going to need to re-light it at some point. In this article, we discuss why that happens and offer safety and maintenance tips.

For a component that’s so vital to heating, the pilot light sure has a reputation for going out at the worst time.

Of course, it’s never a good time for your pilot light to go out. But if it does, you have options to get your system back up and running.

While few newer furnaces have pilot lights today, I’ve dealt with my share of pilot lights. Over the last 30 years, I’ve worked in HVAC as an installation technician, a service technician and a sales professional.

Whether you grew up dealing with pilot lights or recently moved into a home with a pilot light furnace, you’ll likely have to re-light your pilot light at some point.

In this article, we’ll discuss a variety of factors that may cause your pilot light to go out, including when you need and don’t need an HVAC technician.

But just so we’re on the same page, let’s go over your pilot light’s role in heating your home.

What Is a Furnace Pilot Light?

A pilot light is a type of igniter that’s typically found in older furnaces. Some of these furnaces could be as old as 30 years.

Igniters like pilot lights provide the spark to heat your home. When your thermostat sends a signal to your furnace to begin the heating cycle, the gas turns on. Because the pilot light is always lit, it ignites the gas. Then your furnace begins heating your home.

Each year we see fewer and fewer furnaces with standing pilot lights. In Central Ohio, I’d say that only around 5% of the furnaces we see have pilot lights.

Since 2010, many manufacturers have turned to other types of igniters. So if your furnace is newer, it likely doesn't have a pilot light.

What Causes a Pilot Light to Go Out?

A pilot light is a continuous flame. This means that your pilot light should always be lit.

First, let’s talk about the best-case reasons your pilot light can go out. These are easier to address than some of the issues we’ll get to later.

1. Strong Winds

Pilot lights may go out occasionally due to strong winds.

Pilot lights are similar to strong candles. You could extinguish a pilot light by blowing it out.

On particularly windy days, winds and down-drafts can extinguish your pilot light if you have a Type B gas vent or a masonry chimney.

When this happens, you generally just have to re-light the pilot light to solve the problem.

2. Dirty Equipment

Pilot lights may also go out due to the buildup of dust, lint and other debris. As grime builds up, your system may not get the oxygen it needs.

It’s also important to note that your pilot light should burn blue -- that means it’s burning cleanly.

As oxygen becomes less available, your pilot light may burn more yellow. At that point, it can also produce more soot and carbon monoxide.

But you shouldn’t attempt to clean your furnace on your own. Because of the complexity of HVAC systems, a trained HVAC technician should clean your furnace.

We’ll talk about how regular maintenance can help with this later. But your HVAC contractor should clean your furnace during its annual tune-up.

How to Re-light Your Furnace Pilot Light

If your pilot light goes out every now and then, you typically don’t have to worry.

You have two options to re-light it:

Consult the owner’s manual for your furnace, and follow the directions.

Contact an HVAC professional.

If you’re not familiar with re-lighting pilot lights, I recommend consulting an HVAC professional.

Furnaces with pilot lights run on natural gas. If you’ve never lit a pilot light before, it can be dangerous to attempt to re-light it on your own.

Once your pilot light is lit once more, it’s time to figure out if there’s a bigger issue.

A lit furnace.

What If My Pilot Light Keeps Going Out?

If your pilot light refuses to stay lit, you may need to check the integrity of your furnace and ventilation system.

A few common reasons a pilot light may repeatedly go out include:

  • Changes in your ventilation system. Wind and precipitation can shift your ventilation covers, which further exposes your pilot light to the elements.
  • Issues with your thermocouple. A thermocouple is a safety device that senses when your pilot light is on. If your thermocouple is dirty, it may not be able to sense that the pilot is on. As a result, the gas valve turns off. If your system keeps trying to start before turning off again, there could be an issue with your thermocouple.
  • Issues with your gas valve. Your gas valve supplies fuel for your system. If neither your pilot light nor your system will turn start, there could be an issue with your gas valve.
  • Cracks in your heat exchanger. After years of heating up and cooling down, your heat exchanger may crack. These cracks can alter airflow within the system, which can extinguish your pilot light.

You’ll likely be able to check for small changes in your ventilation system, such as a missing rain cap, yourself. But a trained HVAC professional should diagnose more complex issues.

How Much Will It Cost to Fix?

You should be able to replace a Type B vent cap for less than $50 depending on the size of the pipe. But replacing a masonry chimney cap, gas valve or heat exchanger can get a bit pricey.

Here’s how much it would cost to fix these issues:

  • Replacement chimney caps can cost between $35 - $750, depending on the material the cap is made of.
  • Replacement thermocouples can cost between $100 - $250.
  • Replacement gas valves start around $350.
  • Heat exchanger repairs start around $100 but can cost thousands of dollars. Repairing a heat exchanger is the HVAC equivalent of heart surgery: these are labor intensive repairs that require a highly skilled technician.
  • Replacement heat exchangers can cost $1,000 - $2,000 under warranty. But if your furnace’s parts aren’t under warranty, you could pay as much as $3,500 to replace your heat exchanger.

Depending on the brand, a heat exchanger may be covered under warranty for 20 years to the life of your system. It’s also important to remember that parts warranties typically don’t cover labor costs and other fees -- only the cost of the parts.

To check if your system is covered under warranty, you’ll need three things: the brand or manufacturer, your furnace’s model number, and your furnace’s serial number.

You should be able to obtain all of this information from your furnace’s data plate. In older furnaces, data plates are typically located inside the furnace’s cabinet.

To locate your furnace’s data plate, open its front panel. Often, you’ll be able to see the data plate on the left or right inner panels.

Safety & Maintenance Tips

As furnaces age, they may not work as well as they used to. If you have a furnace with a pilot light, your furnace has likely lived a good, long life. But if you’re not ready to replace just yet, let’s talk through safety and maintenance tips for furnaces with pilot lights.

1. Place carbon monoxide detectors near sleeping areas.

A pilot light can generate more carbon monoxide as the system ages. Because carbon monoxide is odorless, carbon monoxide detectors can alert you before you’re in danger of carbon monoxide poisoning.

But make sure that you place carbon monoxide detectors near the areas where you and your family sleep. This way, you’ll be more likely to hear the detectors no matter the time of day.

The CDC recommends using battery-powered carbon monoxide detectors. If you check the batteries when you change your clocks in the spring and fall, you can ensure that your detector is in working order.

If your carbon monoxide detector goes off, leave your home immediately and call 911.

2. Schedule regular maintenance for your system.

Regular maintenance can help systems run smoothly and efficiently for as long as possible.

Although regular tune-ups won’t make your system live forever, they can make a huge difference. Maintenance can identify issues before your system breaks down.

Regular maintenance can also catch high levels of carbon monoxide before they become deadly. During a routine tune-up, an HVAC technician should check your system’s performance. This includes checking how much carbon monoxide your system produces.

Regular maintenance also ensures that your furnace operates efficiently.

Furnaces with pilot lights could operate up to 50-70% efficiently in their prime. Although this is significantly less efficient than modern furnaces, you can conserve as much of that efficiency as possible with maintenance.

Your HVAC partner should clean your system during a furnace tune-up, which can play a large role in ensuring your system is operating properly. As your heat exchanger collects dirt, your system has to work harder to produce heat. This increases wear and tear on your system.

Because of the complexity of your system, you should avoid DIY maintenance unless you’re changing a filter.

You should schedule maintenance for your home twice a year: once before the cooling season and once before the heating season.

This ensures that both your heating and cooling systems can operate properly when you need them most.

A technician working on a furnace.

When to Repair and When to Replace

Even if your furnace is heating your home now, that doesn’t mean it can forever.

Repairs can keep an older system going for a while. But eventually repairing your furnace becomes less cost-effective. The cost of repairs can add up, especially as a system ages.

Even if you’re hesitant to replace your furnace right now, it never hurts to know how much a replacement costs. When you know how much a replacement will cost, you can make better-informed decisions.

Let’s say, for example, that your HVAC contractor tells you that it’ll cost $2,000 to repair your furnace this time.

For many homeowners, $2,000 is a lot of money. Depending on the replacement, $2,000 could be as much as 67% of the final price tag (including labor and other fees) on a new furnace.

When you know the cost of a replacement furnace, you can decide whether it’s better to continue repairing or go ahead and replace your furnace.

As you gather information, these articles could help:

And if you’d like to schedule a tune-up or a free estimate, we’d love to meet with you!

At Fire & Ice, we believe in educating homeowners so they can make the best decisions for themselves and their homes. This is the mindset that our service technicians and comfort specialists both offer our customers.

If you live in Central Ohio, click the button below to contact us. We look forward to speaking with you!

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