Where Is the Pilot Light on a Furnace: Locating and Troubleshooting

The pilot light on a furnace is a small but essential flame that ignites the main burner. Knowing where the pilot light is located and how to access it helps with basic troubleshooting, safe relighting, and identifying potential problems. This article explains typical pilot light locations, steps to find and relight it, safety precautions, and when to contact a professional.

Furnace Type	Typical Pilot Light Location	Access Notes
Natural Draft (Older Furnaces)	Lower front panel, near burner assembly	Panel may lift or slide off; pilot near gas valve
Direct-Vent/Sealed Combustion	Behind access panel or control cover	Often requires removing screws; pilot visible through small window
Wall Furnaces	Front lower grille or inside front panel	Small control door; pilot often near thermostat knob
Gas Boiler/Space Heater	Lower burner compartment	May require lighting key or built-in ignitor

How The Pilot Light Works

The pilot light is a continuously burning flame that ignites the furnace’s main burner when the thermostat calls for heat. It is supplied by a small gas line connected to a gas valve and often monitored by a thermocouple or flame sensor to ensure safe operation.

Key Components:

• Pilot Orifice: Controls gas flow to the pilot flame.
• Thermocouple/Flame Sensor: Detects heat from the flame and signals the gas valve.
• Gas Valve/Control Knob: Includes OFF, PILOT, and ON positions for lighting and operation.

Common Furnace Types And Where The Pilot Light Is Located

Different furnace designs place the pilot light in predictable spots. Identifying the furnace type narrows down the search and reduces the chance of accidentally interfering with other components.

Older Natural Draft Furnaces

Older furnaces often have the pilot light mounted near the burner assembly in the lower front compartment. The front access panel usually removes easily, exposing the burner and pilot assembly.

Direct-Vent Or Sealed-Combustion Furnaces

These modern units isolate combustion air from indoor air. The pilot, if present, sits behind a sealed access panel or under the control cover. Some direct-vent models use electronic ignition instead of a standing pilot.

Wall Furnaces And Space Heaters

Wall-mounted gas furnaces typically have a small front access door or grille; the pilot light is positioned near the ignition assembly and pilot adjustment screw for easy service.

Gas Boilers And Combination Units

Boilers have a burner compartment at the bottom. The pilot is usually inside that compartment near the gas manifold. Modern boilers may use electronic ignition rather than a standing pilot light.

Step-By-Step: Where To Look For The Pilot Light

Locating the pilot light safely requires a systematic approach. Before attempting to find or relight a pilot, always follow safety steps and manufacturer instructions.

1. Turn Off The Furnace: Set the thermostat to OFF and turn the furnace control knob to OFF, if present.
2. Allow Cooling Time: Wait several minutes for the furnace to cool before removing panels.
3. Locate The Access Panel: Check the lower front of the furnace for a removable panel, screws, or clips.
4. Identify The Burner Compartment: Remove the panel to expose the burner assembly, gas valve, and pilot tube.
5. Look For The Pilot Assembly: The pilot is a small metal tube with a fixed flame or an opening where a flame should be visible. It sits next to the main burners.
6. Check For A Viewing Window: Some furnaces have a small glass or plastic window allowing visual inspection without opening the compartment.

Tip: If the furnace has an internal control panel with a knob labeled OFF/PILOT/ON, the pilot assembly will be nearby.

Safety Precautions Before Lighting Or Inspecting

Working with gas appliances carries risk. Observing safety precautions protects occupants and prevents damage to the furnace.

• Ventilation: Ensure adequate fresh air flow before opening the furnace compartment.
• Gas Smell: If natural gas is detected, immediately evacuate the area and call the gas utility or emergency services. Do not light the pilot or operate electrical switches.
• Turn Off Power: Shut off electrical power to the furnace at the breaker if servicing internal components.
• Read The Manual: Consult the furnace manual for model-specific instructions on pilot location and lighting.
• Use Proper Tools: Use a long-reach lighter or match if the pilot is hard to reach, and avoid using aerosol sprays or flammable materials near the unit.

How To Relight A Pilot Light Safely

Many homeowners need to relight a pilot periodically. Follow the furnace’s instructions exactly. The general procedure below applies to common standing pilot systems.

1. Turn The Gas Control To OFF And Wait Five Minutes To Clear Accumulated Gas.
2. Turn The Control To PILOT And Hold It Down To Allow Gas To Flow To The Pilot.
3. While Holding The Control, Use A Long Lighter To Ignite The Pilot Flame.
4. Hold The Control For 30–60 Seconds After Ignition To Heat The Thermocouple.
5. Release The Control Slowly. If The Pilot Stays Lit, Turn The Control To ON.
6. Replace Panels And Restore Power, Then Confirm The Furnace Cycles Normally.

Warning: If the pilot will not stay lit after several attempts, stop and proceed to troubleshooting or call a trained technician.

Troubleshooting Common Pilot Light Problems

Identifying why a pilot light won’t stay lit helps determine whether the issue is a simple fix or requires professional service.

Pilot Won’t Stay Lit

Common causes include a faulty thermocouple, a dirty pilot orifice, or a weak pilot flame. A weak flame may fail to heat the thermocouple sufficiently to keep the gas valve open.

Pilot Light Is Yellow Or Sooty

A healthy pilot flame is blue. A yellow or sooty flame indicates incomplete combustion, possible blockage, or incorrect gas pressure. This issue can produce carbon monoxide and requires immediate attention.

Pilot Keeps Going Out During Windy Conditions

Drafts or improper venting can extinguish the pilot. Ensure vents and flues are intact and free from obstructions, and check that exterior vent caps are secure.

Pilot Smells Like Gas Before Lighting

A persistent gas odor before lighting the pilot suggests a leak. Stop, ventilate the area, and contact the gas company or a licensed technician immediately.

Maintenance Tips To Keep The Pilot Light Reliable

Regular maintenance reduces pilot problems and extends furnace life. Many tasks can be performed by homeowners, while others should be left to professionals.

• Inspect Annually: Have a qualified technician perform a yearly inspection and tune-up, including cleaning the pilot orifice and checking the thermocouple.
• Keep Vents Clear: Remove debris and snow from outdoor vents to prevent backdrafts and blockages.
• Replace Worn Components: Thermocouples and pilot assemblies degrade over time; replace them if the pilot becomes unreliable.
• Clean Burner Area: Dust and dirt can affect combustion; keep the burner compartment clean during regular maintenance.

When To Call A Professional

Some pilot light and furnace issues require professional diagnosis and repair. Calling a licensed HVAC technician ensures safe, code-compliant service.

• Repeated Pilot Failure After Basic Troubleshooting
• Yellow Pilot Flame Or Evidence Of Soot
• Strong Gas Odors Or Suspected Leaks
• Unusual Noises Or Furnace Cycling Problems
• Issues With The Venting System Or Carbon Monoxide Concerns

Note: Working on gas valves, sealed combustion systems, or complex controls should always be performed by a licensed technician.

How To Identify If A Furnace Uses A Standing Pilot Or Electronic Ignition

Knowing whether a furnace uses a standing pilot or an electronic ignition affects how pilot issues are approached. Standing pilots are constant flames; electronic ignitions use spark or hot-surface devices.

• Standing Pilot Indicators: Small, constantly burning flame visible at the burner area and a control knob labeled OFF/PILOT/ON.
• Electronic Ignition Indicators: No visible pilot flame, and rapid electronic clicking or glow when the thermostat calls for heat.

Frequently Asked Questions About Pilot Light Location

Can The Pilot Light Be Outside The House?

Some sealed direct-vent systems draw combustion air from outdoors, but the standing pilot itself remains within the furnace or appliance housing. Exterior pilot lights are uncommon and typically restricted to specific outdoor-rated appliances.

Is It Safe To Leave The Pilot On All The Time?

Standing pilots consume a small amount of gas continuously. While generally safe when functioning properly, some homeowners opt for furnaces with electronic ignition to eliminate continuous gas usage and reduce energy waste.

How Much Gas Does A Pilot Light Use?

Pilot lights consume a modest amount of gas—typically between 20 and 120 therms per year depending on the pilot orifice size. Replacing a standing pilot with electronic ignition can lower fuel use.

Resources And Next Steps

When locating a pilot light, always consult the furnace owner’s manual or label inside the access panel for model-specific guidance. For persistent problems, use local directories or utility provider recommendations to find licensed HVAC professionals.

Key Takeaway: The pilot light location varies by furnace type, but it is usually in the lower burner compartment behind an access panel. Safe inspection, proper relighting technique, and routine maintenance are essential for reliable operation.