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Ignite with Ease: Your Step-by-Step Guide on How to Light a Gas Furnace

EPA Certified Technician John conducting a furnace repair. Technician John is relighting a gas furnace.

Have you ever found yourself in the middle of a cold winter night, only to discover that your gas furnace pilot light has gone out? Panic no more, as this step-by-step guide will teach you how to light a gas furnace pilot light with ease, ensuring a warm and cozy home for you and your family.

Key Takeaways

  • Understand your gas furnace’s pilot light system and its role in safety.

  • Prepare adequately before relighting the pilot light to ensure proper functioning.

  • Seek professional furnace repair if uncertain when dealing with common issues such as wind and drafts or adjusting the thermocouple.

Understanding Your Gas Furnace’s Pilot Light System

Gas furnace with ignited pilot light

The pilot light system plays a key role in your gas furnace, igniting the burners and starting the heating process. Understanding the role of the pilot light and the differences between electronic ignition systems and standing pilot lights will help you troubleshoot and maintain your furnace efficiently.

The Role of the Pilot Light

The pilot light’s primary function is to ignite the natural gas supplied to the unit from the main burner, thus initiating the heating process. This small, continuous flame serves as a safety mechanism, as it heats the thermocouple bulb located next to the pilot flame. The thermocouple ensures that the gas valve remains open as long as the pilot light is lit, preventing gas from flowing if the pilot light is extinguished.

Although the thermocouple is an essential safety component, it can fail over time, leading to a non-functioning pilot light. Understanding the function of the pilot light aids in identifying possible problems and maintaining peak furnace performance.

Electronic Ignition Systems vs. Standing Pilot Lights

While older furnaces typically use standing pilot lights, modern furnaces often incorporate electronic ignition systems. Standing pilot lights consist of a continuous flame, which ignites the gas entering the furnace when the heating system is activated.

Electronic ignition systems, such as electric ignition, do not use pilot lights and offer increased fuel efficiency, higher overall efficiency, and improved reliability.

Preparing to Relight Your Gas Furnace Pilot Light

Before attempting to relight your gas furnace pilot light, it is important to take necessary precautions and get your furnace ready for the relighting process. This includes ensuring proper gas flow and pressure, clearing the pilot light opening, and adhering to safety tips.

Ensuring Gas Flow and Pressure

To ensure proper natural gas, flow and pressure, and to avoid excess gas, follow these steps:

  1. Visually inspect the gas vent or pilot opening for any obstructions.

  2. Turn off the gas supply.

  3. Turn the gas regulator knob to the “Pilot” position before attempting to relight the pilot light.

Depress and hold the gas valve or reset button to initiate gas flow, and use a long-stemmed lighter or match to ignite the pilot light.

Clearing the Pilot Light Opening

A clean pilot light opening is required for efficient ignition. Indications that the pilot light opening requires clearing include:

  • A pilot light not displaying a bright blue color

  • Air being emitted from the vents without a temperature increase

  • A pilot light remaining illuminated even when the furnace is not in use

To clean the pilot light opening, use a paper clip, wire brush, or stranded wire to remove any debris or accumulation from the pilot tube.

Tips for Safety

Before relighting the pilot light, turn off the gas supply and allow any remaining gas to dissipate for at least five minutes. The significance of allowing at least five minutes for the gas to dissipate from the chamber prior to relighting the pilot light is to prevent the ignition of any surplus gas.

When relighting the pilot light, follow these safety precautions:

  • Wear safety glasses to protect your eyes

  • Use a long-handled match or long-reach lighter for safe ignition

  • Use a flashlight for improved visibility in the area

These safety precautions will help ensure a secure proceeding when you relight the pilot light securely and effectively.

Detailed Steps to Light Your Gas Furnace Pilot

Step-by-step instructions for lighting the gas furnace pilot

With your furnace prepared, it’s time to proceed with the step-by-step process to relight the pilot light. This includes locating the pilot light assembly, using the reset button switch and gas valve, and igniting the flame.

Locating the Pilot Light Assembly

To locate the pilot light assembly, follow these steps:

  1. Look for a small flame where the gas lines point into the furnace.

  2. The pilot light assembly is typically positioned at the lower end of the furnace, alongside a knob.

  3. If the furnace is not antiquated, the pilot light assembly is likely situated there.

  4. If you can’t locate it, consult the furnace’s manual or the manufacturer’s website for assistance.

Using the Reset Button and Gas Valve

Once you’ve located the pilot light assembly, follow these steps to relight the pilot light:

  1. Turn off the gas valve and allow the gas to disperse.

  2. Turn the valve to ‘Pilot’.

  3. Press and hold the valve button.

  4. Use a long-stemmed lighter to ignite the pilot light.

  5. Maintain the button in a depressed state for approximately one minute to enable the pilot light to become steady.

Once the pilot light is stable, release the button and turn the knob on the gas valve to ensure proper operation.

Igniting the Flame

Use a long lighter to a long match to ignite the flame. Bring the flame close to the pilot opening. As the pilot light ignites, hold down the reset button until the flame turns a solid blue hue. This indicates that the pilot light is burning steadily and you can release the reset button.

With the pilot light relit, your furnace should now be functioning correctly.

Maintaining Your Pilot Light and Furnace Running Smoothly

Maintaining a gas furnace pilot light and smooth furnace operation

To keep your furnace running smoothly and efficiently, it’s important to maintain your pilot light and monitor the flame and heat output. Regular cleaning and maintenance will not only prolong the life of your furnace but also ensure optimal performance.

Regular Cleaning and Maintenance

An annual cleaning of your furnace is necessary for enhancing efficiency, preventing gas leaks, achieving optimal performance, ensuring cleaner air, and saving costs. To clean your gas furnace pilot light, follow these steps:

  1. Switch off the furnace.

  2. Use a paper clip or wire brush to remove any debris from the mouth of the pilot light.

  3. Gently clean the thermocouple with steel wool to eradicate any soot.

Regular cleaning and maintenance can increase the longevity of your gas furnace. Neglecting maintenance can result in a shorter lifespan, whereas regular servicing and cleaning can help detect and address problems before they become significant repairs.

It is advised to have routine, annual maintenance and occasional cleaning to ensure the durability of the furnace.

Monitoring Flame and Heat Output

Observing the pilot light flame and heat output is necessary for optimal furnace performance. A blue flame indicates efficient combustion and optimal heat production. To determine the heat output of your gas furnace, measure the temperature rise on the supply side of the furnace, just above the A coil, or consult the AFUE (Annual Fuel Utilization Efficiency) percentage listed on the furnace’s nameplate.

Infrared temperature pyrometers and temperature sensors can be used for temperature monitoring.

Troubleshooting Common Pilot Light Issues

Despite your best efforts, you may still encounter some common pilot light issues. Knowing how to troubleshoot these issues, such as dealing with wind and drafts or adjusting the thermocouple, will help you maintain your furnace’s performance and ensure a warm and comfortable home.

Dealing with Wind and Drafts

Wind and drafts can adversely affect your pilot light. Drafts in a furnace may be attributed to:

  • Poor insulation

  • Fluctuations in indoor and outdoor temperatures

  • Obstruction of the vent

  • Wind

  • The ‘stack effect’

  • Combustion

  • Mechanical extraction fans

To identify if drafts are causing pilot light issues, look for flickering or wavering flames, inefficient burning flames, or accumulation of dirt near the pilot light. Ensuring proper insulation, sealing cracks, and maintaining proper airflow can help minimize the impact of drafts on your pilot light.

Adjusting the Thermocouple

A defective thermocouple is the most prevalent cause of pilot light difficulties. To adjust a thermocouple in a gas furnace, follow these steps:

  1. Open the access cover.

  2. Locate the thermocouple.

  3. Loosen the mounting screws.

  4. Remove the old thermocouple.

  5. Install the new thermocouple.

  6. Connect the gas supply to the furnace.

Turn on the gas and power to the furnace after waiting at least half an hour for the thermocouple to cool off. If you’re unsure about adjusting the thermocouple, it is advised to seek professional help.

When to Seek Professional Furnace Repair

Certain furnace issues may not be suitable for a DIY solution. In these situations, seeking professional furnace repair services is advisable. Common issues that necessitate professional intervention include:

  • High winds or downdraft

  • Inefficient pilot flame caused by low gas pressure or a blocked orifice

  • A flame that is set too small

  • A dirty air filter

  • A faulty thermostat

  • A faulty pilot light

  • A problem with the ignition system

  • A broken thermocouple

  • Poor location and airflow problems

  • Dirt build-up on the gas intake valve.


In conclusion, knowing how to light your gas furnace pilot light is an essential skill for homeowners. By following this step-by-step guide, you can ensure a warm and comfortable home during those cold winter months. Remember to maintain your pilot light and furnace, troubleshoot common issues, and seek professional furnace repair when needed. Stay warm and cozy!

Frequently Asked Questions

How do I relight my gas furnace?

Turn off the power and gas supply to the furnace, then locate and relight the pilot light using a long-stemmed lighter. Hold down the reset button while lighting the pilot light, and release the button once it is burning steadily. Finally, turn the gas and furnace back on.

Can I light my furnace myself?

By turning the knob to “Pilot” and then using a lighter or match to light the pilot light, you can safely light the pilot on your furnace yourself.

What is the ideal flame color for a gas furnace pilot light?

The ideal flame color for a gas furnace pilot light is blue, indicating efficient combustion and optimal heat production.

How often should I clean my gas furnace?

It is recommended to clean your gas furnace at least once a year for optimal performance and to prolong its life.

What are some common issues that may require professional furnace repair?

Common issues that may require professional furnace repair include high winds or downdraft, inefficient pilot flame, a flame set too small, a dirty air filter, faulty thermostat, faulty pilot light, ignition system issue, broken thermocouple, poor location and airflow problems, and dirt build-up on the gas intake valve.

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