Where is the Pilot Light on a Furnace and what does it do
If you’ve ever had your furnace stop producing heat in the middle of winter, one of the first things an HVAC technician will check is the pilot light. The pilot light is a small but essential part of older gas furnaces that ensures your heating system ignites safely and efficiently.
Understanding where to find the pilot light on your furnace, what it does, and how to safely relight it can help you troubleshoot simple heating problems — and know when it’s time to call a professional.
What Is a Furnace Pilot Light?A pilot light is a small flame that continuously burns inside older gas-powered furnaces, water heaters, or boilers. Its main purpose is to ignite the main burners when your furnace turns on.
Think of it like a small “starter flame.” When your thermostat calls for heat, the gas valve opens and releases fuel into the burners. The pilot light then ignites that gas, starting the combustion process that produces warm air for your home.
Modern furnaces, especially those built after the early 2000s, often don’t use a standing pilot light. Instead, they rely on electronic ignition systems such as a hot surface igniter (HSI) or spark ignition. However, many older homes still use traditional furnaces that depend on a manual pilot light.
Where Is the Pilot Light Located on a Furnace?The exact location of the pilot light varies slightly depending on the make and model of your furnace, but it’s generally found inside the main burner compartment — usually near the bottom front of the unit.
Here’s how to find it safely:
What Does the Pilot Light Do?The pilot light acts as the ignition source for your furnace’s gas burners. Here’s how it works in a heating cycle:
The pilot light also works with a thermocouple, a small safety device that detects whether the pilot flame is burning. If the thermocouple doesn’t sense heat, it automatically shuts off the gas supply to prevent unburned gas from leaking into your home.
Why Does the Pilot Light Go Out?Pilot lights can go out for several reasons, most of them related to airflow or fuel supply:
How to Relight a Pilot Light (Safely)If your furnace’s pilot light goes out, you can usually relight it yourself — but always follow safety precautions.
Before you start:
When Should You Replace a Pilot Light System?If you find yourself relighting the pilot light often, it may be a sign that your furnace is aging. Modern furnaces with electronic ignition systems are far more energy-efficient and reliable.
Electronic ignition eliminates the need for a constantly burning flame, saving gas and reducing wear on components. If your furnace is more than 15–20 years old, consider upgrading to a newer model with an automatic ignition system.
Pilot Light Safety Tips
The pilot light may be small, but it’s the heart of an older gas furnace. Its steady flame ensures your heating system starts safely, keeps your home warm, and prevents dangerous gas buildup.
Knowing where to find it and how it works helps you handle simple furnace issues — but always prioritize safety. If the pilot won’t stay lit or you notice gas smells, call a licensed HVAC professional right away.
Keeping your pilot light in good working order not only ensures comfort but also keeps your family safe through the coldest months of the year.
Frequently Asked Questions on Furnace Pilot LightQ1: How do I know if my furnace has a pilot light or electronic ignition?
Check for a small gas control knob labeled “ON / OFF / PILOT.” If you see one, your furnace uses a pilot light. Modern furnaces typically lack this and use electronic igniters instead.
Q2: Why won’t my pilot light stay lit?
The most common reason is a faulty thermocouple, which shuts off the gas if it doesn’t detect heat. Dirty or blocked pilot tubes can also cause the flame to go out.
Q3: Is it safe to relight a pilot light myself?
Yes — as long as you follow the furnace manufacturer’s instructions carefully and don’t smell gas. If you’re unsure or uncomfortable, call an HVAC professional.
Q4: Can I leave my pilot light on year-round?
You can, but many homeowners turn it off during summer to save gas. Just be sure to relight it safely before the heating season.
Understanding where to find the pilot light on your furnace, what it does, and how to safely relight it can help you troubleshoot simple heating problems — and know when it’s time to call a professional.
What Is a Furnace Pilot Light?A pilot light is a small flame that continuously burns inside older gas-powered furnaces, water heaters, or boilers. Its main purpose is to ignite the main burners when your furnace turns on.
Think of it like a small “starter flame.” When your thermostat calls for heat, the gas valve opens and releases fuel into the burners. The pilot light then ignites that gas, starting the combustion process that produces warm air for your home.
Modern furnaces, especially those built after the early 2000s, often don’t use a standing pilot light. Instead, they rely on electronic ignition systems such as a hot surface igniter (HSI) or spark ignition. However, many older homes still use traditional furnaces that depend on a manual pilot light.
Where Is the Pilot Light Located on a Furnace?The exact location of the pilot light varies slightly depending on the make and model of your furnace, but it’s generally found inside the main burner compartment — usually near the bottom front of the unit.
Here’s how to find it safely:
- Turn Off the Furnace: Always switch the furnace to “off” before opening any panels.
- Remove the Access Panel: Most furnaces have a small metal or plastic cover at the bottom front. Remove it carefully.
- Locate the Gas Control Valve: You’ll usually see a small gas valve labeled “On / Off / Pilot.” This is connected to a small metal tube.
- Follow the Small Tube: The thin tube leads to the pilot assembly, which includes the pilot orifice, the thermocouple, and the flame itself.
- Find the Flame (If Lit): If your pilot is working, you’ll see a small, steady blue flame about one to two inches high.
What Does the Pilot Light Do?The pilot light acts as the ignition source for your furnace’s gas burners. Here’s how it works in a heating cycle:
- Thermostat Calls for Heat: When your home drops below your set temperature, the thermostat signals the furnace to start.
- Gas Valve Opens: The furnace’s control system opens the gas valve, allowing natural gas or propane to flow to the burners.
- Pilot Flame Ignites the Gas: The small, always-burning pilot flame lights the gas flowing to the burners.
- Burners Produce Heat: The flames heat the heat exchanger, which warms the air that’s blown through your ducts.
The pilot light also works with a thermocouple, a small safety device that detects whether the pilot flame is burning. If the thermocouple doesn’t sense heat, it automatically shuts off the gas supply to prevent unburned gas from leaking into your home.
Why Does the Pilot Light Go Out?Pilot lights can go out for several reasons, most of them related to airflow or fuel supply:
- Drafts or Wind: A strong draft near the furnace can blow out the flame.
- Dirty Pilot Orifice: Dust or soot buildup can block gas flow to the pilot.
- Faulty Thermocouple: A worn-out thermocouple may incorrectly signal the gas valve to close.
- Gas Supply Issues: Low gas pressure or a temporary outage can extinguish the flame.
- Moisture or Corrosion: Rust or water inside the combustion chamber can interfere with ignition.
How to Relight a Pilot Light (Safely)If your furnace’s pilot light goes out, you can usually relight it yourself — but always follow safety precautions.
Before you start:
- Turn the furnace switch to OFF.
- Wait at least 5 minutes to allow any lingering gas to dissipate.
- If you smell gas or suspect a leak, do not attempt to relight it. Leave the house immediately and call your gas company or a licensed HVAC professional.
- Locate the Gas Control Valve. It’s usually labeled “ON,” “OFF,” and “PILOT.”
- Turn the Valve to PILOT.
- Press and Hold the Reset Button. This allows gas to flow to the pilot assembly.
- Use a Long Lighter or Match. While holding the reset button, ignite the pilot flame.
- Hold for 30 Seconds. Keep holding the button to heat the thermocouple, which confirms the flame is stable.
- Release the Button and Turn to ON. The pilot should remain lit.
- Replace the Access Panel. Restore power and set your thermostat to call for heat.
When Should You Replace a Pilot Light System?If you find yourself relighting the pilot light often, it may be a sign that your furnace is aging. Modern furnaces with electronic ignition systems are far more energy-efficient and reliable.
Electronic ignition eliminates the need for a constantly burning flame, saving gas and reducing wear on components. If your furnace is more than 15–20 years old, consider upgrading to a newer model with an automatic ignition system.
Pilot Light Safety Tips
- Never leave the access panel off after lighting the pilot — it can cause unsafe drafts.
- Do not use random flames (like a candle or paper) to light it — use a long BBQ lighter.
- Schedule annual furnace maintenance. A technician will clean the pilot assembly, inspect the thermocouple, and check for leaks.
- Install a carbon monoxide detector near your furnace for added safety.
The pilot light may be small, but it’s the heart of an older gas furnace. Its steady flame ensures your heating system starts safely, keeps your home warm, and prevents dangerous gas buildup.
Knowing where to find it and how it works helps you handle simple furnace issues — but always prioritize safety. If the pilot won’t stay lit or you notice gas smells, call a licensed HVAC professional right away.
Keeping your pilot light in good working order not only ensures comfort but also keeps your family safe through the coldest months of the year.
Frequently Asked Questions on Furnace Pilot LightQ1: How do I know if my furnace has a pilot light or electronic ignition?
Check for a small gas control knob labeled “ON / OFF / PILOT.” If you see one, your furnace uses a pilot light. Modern furnaces typically lack this and use electronic igniters instead.
Q2: Why won’t my pilot light stay lit?
The most common reason is a faulty thermocouple, which shuts off the gas if it doesn’t detect heat. Dirty or blocked pilot tubes can also cause the flame to go out.
Q3: Is it safe to relight a pilot light myself?
Yes — as long as you follow the furnace manufacturer’s instructions carefully and don’t smell gas. If you’re unsure or uncomfortable, call an HVAC professional.
Q4: Can I leave my pilot light on year-round?
You can, but many homeowners turn it off during summer to save gas. Just be sure to relight it safely before the heating season.
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