How to Relight a Furnace Pilot Light Safely

The furnace pilot light ensures continuous ignition for many older gas furnaces; when it goes out, relighting it is often a safe, manageable task. This article explains step-by-step how to relight a furnace pilot light, outlines safety precautions, diagnostics for common problems, and guidance on when to call a professional. Follow manufacturer instructions first and always prioritize safety when working with gas appliances.

Topic	Quick Takeaway
Safety First	Turn off gas and power; ventilate area; avoid flames if gas odor is present.
Tools Needed	Flashlight, long lighter or match, wrench (if access panels require), owner’s manual.
Basic Steps	Shutoff, wait, set control to “pilot,” depress button while lighting, hold per instructions.
Troubleshooting	Thermocouple issues, clogged pilot orifice, gas supply problems.
When To Call Pro	Persistent outages, gas smell, malfunctioning controls, complex repairs.

Understanding Pilot Light Systems

Many older furnaces use a continuously burning pilot light to ignite the main burners when heat is needed. Newer furnaces often use electronic ignition systems that eliminate a standing pilot light. Identifying whether the furnace uses a pilot light is the first step before attempting to relight anything.

Key components include the pilot assembly, thermocouple or thermopile, gas valve with pilot setting, and control knob or switch. The thermocouple senses heat from the pilot and keeps the gas valve open; if the thermocouple fails, the pilot cannot stay lit.

Safety Precautions Before Relighting

Safety must guide any interaction with gas appliances. Before attempting to relight a furnace pilot light, ensure there is no strong gas odor in the area. If gas is detected, evacuate immediately and call the gas company or emergency services from a safe location.

Recommended safety steps: Turn off the furnace’s power switch or circuit breaker, close the gas control knob if instructed by the manual, open windows for ventilation, have a flashlight and long-stem lighter or match. Do not use mobile phones or electrical switches near suspected gas leaks.

Tools And Supplies Needed

• Manufacturer’s furnace manual (or model-specific instructions)
• Long-stem lighter or long fireplace match
• Flashlight for visibility in the furnace compartment
• Adjustable wrench or screwdriver to open access panels if necessary
• Work gloves and safety glasses for protection

Step-By-Step Procedure To Relight The Pilot Light

Locate The Pilot Assembly And Control

First, locate the pilot assembly and the gas control knob or switch on the furnace. The assembly is typically near the burners; the control knob will have positions labeled OFF, ON, and PILOT.

Turn Off Gas And Power

Set the gas control to OFF and turn off the furnace power at the switch or breaker. Wait at least five minutes to let any accumulated gas dissipate, or longer if the area smelled strongly of gas. Ventilate by opening doors or windows.

Set Control To Pilot And Light

After the wait, turn the gas control knob to the PILOT position. Depress and hold the pilot button or knob to allow gas flow to the pilot orifice while using a long-stem lighter or match to ignite the pilot. Continue holding the button for 20–60 seconds per manufacturer guidance to allow the thermocouple to heat.

Release And Verify

Slowly release the pilot button. If the pilot remains lit, turn the control knob to the ON position and restore power to the furnace. Observe the furnace through a full heat cycle to verify ignition of the main burners and normal operation.

If The Pilot Won’t Light

If the pilot fails to light, repeat the wait and attempt sequence once or twice. If the flame ignites but does not stay lit when releasing the button, the thermocouple may be weak, misaligned, dirty, or failing.

Troubleshooting Common Pilot Light Problems

Thermocouple Or Thermopile Issues

The thermocouple generates a voltage while heated by the pilot flame to keep the gas valve open. Common symptoms of a bad thermocouple include a pilot that lights but will not stay lit or a furnace that shuts off shortly after ignition. Inspect for loose connections, corrosion, or a flame not fully enveloping the thermocouple.

Clogged Pilot Orifice

Dirt, dust, and spider webs can clog the pilot orifice and weaken the flame. A weak flame may be below the thermocouple sensor, causing shutoff. Cleaning requires turning off the gas and using compressed air or a thin wire; if unsure, consult a technician to avoid damage.

Gas Supply Or Valve Problems

If other gas appliances are affected or the furnace has weak or no gas flow, the issue could be with the gas supply, gas meter, shutoff valve, or the furnace’s control valve. Verify other gas appliances operate and check the main shutoff valve. If gas supply problems are suspected, contact the gas utility or a licensed technician.

Pilot Flame Shape And Color

A healthy pilot flame is steady and blue with a small inner blue cone. A yellow, flickering, or oversized flame may indicate combustion issues, dirt, or draft problems. These conditions can affect thermocouple heating and overall safety, so professional inspection is recommended.

Maintenance Tips To Prevent Future Pilot Outages

• Schedule annual furnace inspections and cleanings by a licensed HVAC technician to check the pilot assembly, burners, and gas controls.
• Keep the area around the furnace clean and free of dust and debris that can enter the pilot assembly.
• Check and replace a weak or failing thermocouple rather than repeatedly relighting the pilot; replacements are inexpensive when performed correctly.
• Consider upgrading to an electronic ignition or a newer high-efficiency furnace when repairs become frequent or costly.

When To Call A Professional

Some situations require immediate professional attention. Call a licensed HVAC technician or the gas company if there is a persistent gas smell, repeated pilot outages despite proper relighting, visible damage to gas lines or components, faulty control valves, or uncertainty about safely performing tasks.

Professionals can perform accurate diagnostics, replace thermocouples, clean pilot orifices safely, and advise on whether a furnace upgrade is more economical than repeated repairs.

Safety Signs And Gas Leak Protocol

If a strong gas odor is present, do not attempt to relight the pilot. Evacuate the home immediately, avoid operating electrical switches or phones, and call the gas company’s emergency number or 911 from a safe distance. Natural gas has an additive odorant to aid detection; any suspected leak should be treated as an emergency.

Upgrading From Pilot Lights To Electronic Ignition

Many homeowners consider switching from a standing pilot to electronic ignition or a direct spark system when older furnaces require frequent repairs. Electronic ignition improves efficiency by eliminating continuous gas consumption and reduces maintenance related to pilot assemblies and thermocouples.

An HVAC professional can assess compatibility, cost, and feasibility; in some cases, a complete furnace replacement may be recommended for safety and energy savings.

Frequently Asked Questions

How Long Should The Pilot Button Be Held?

Typically 20–60 seconds as specified by the furnace manual to allow the thermocouple to heat and register the flame. Holding shorter may not heat the thermocouple adequately, preventing the gas valve from staying open.

Why Does The Pilot Keep Going Out?

Common causes include a faulty thermocouple, clogged pilot orifice, drafts or venting problems, gas supply issues, or improper flame shape. Repeated outages warrant professional diagnosis.

Is It Dangerous To Relight A Pilot Light?

When performed correctly and without a gas leak, relighting a pilot light is generally safe. Follow manufacturer instructions, ventilate the area, and stop immediately if a gas smell is present.

Can A Homeowner Replace A Thermocouple?

Some homeowners with basic mechanical skills can replace a thermocouple, but proper gas appliance work requires caution. If uncertain, use a licensed technician to ensure safe and code-compliant installation.

Summary Of Key Steps

• Identify whether the furnace uses a pilot light.
• Turn off gas and power, ventilate, and wait if gas odor is present.
• Set control to PILOT, hold the button, and light with a long lighter.
• Hold per instructions, release, then set to ON and restore power.
• Troubleshoot thermocouple, orifice, and gas supply if the pilot will not stay lit.
• Call a pro for gas odors, repeated failures, or complex repairs.

Relighting a furnace pilot light is a useful homeowner skill when done carefully and in accordance with safety guidelines and the furnace manufacturer’s instructions. For persistent issues, professional inspection ensures safety and reliable operation.