How to Relight a Pilot Light on a Furnace Safely

The pilot light on a furnace is a small flame that ignites the main burner. When it goes out, the furnace stops heating and relighting must be done carefully to avoid gas hazards. This article guides readers through safe relighting procedures for common furnace types, troubleshooting tips, and when to call a professional. Safety is emphasized throughout to reduce risks associated with natural gas or propane.

Item	Quick Summary
Tools Needed	Long-reach lighter or match, flashlight, screwdriver, owner’s manual
Common Causes	Drafts, thermocouple failure, sediment, gas valve or control issues
When To Call A Pro	Smell Of Gas, Repeated Outages, Thermocouple Replacement, Complex Repairs

How Pilot Light Systems Work

Two pilot systems are common: standing pilot (a continuously burning pilot) and electronic ignition (uses an electric igniter or hot surface igniter). Standing pilots use a thermocouple to sense heat and keep the gas valve open. Electronic systems light the main burner automatically and usually do not have a continuously burning flame.

Safety Precautions Before Relighting

Before any relight attempt, check for the odor of gas. If gas is present, evacuate immediately and call the gas company or emergency services. Never relight a pilot when gas odor is detected.

Turn off the furnace and the gas supply at the control valve. Allow the area to ventilate for several minutes to clear any accumulated gas. Keep open flames and electrical switches away until ventilation is complete.

Read the furnace manufacturer’s instructions in the owner’s manual. Different units have specific relighting sequences and safety features. If the manual is unavailable, look up the model number online for guidance.

Tools And Materials Needed

• Long-reach utility lighter or long match
• Flashlight or headlamp
• Screwdriver or nut driver to access pilot assembly
• Needle-nose pliers for small adjustments
• Replacement thermocouple or pilot assembly (if troubleshooting)

Relighting A Standing Pilot Furnace: Step-By-Step

Standing pilot furnaces are the ones most users will encounter because they have a visible pilot flame. Follow these steps carefully and proceed only if there is no gas smell.

Step 1: Turn Off The Gas Supply

Locate the gas control knob on the furnace control panel and turn it to the “Off” position. Wait at least five minutes to allow residual gas to disperse.

Step 2: Open The Access Panel

Remove the furnace access panel using a screwdriver or by unlatching. Use a flashlight to locate the pilot assembly, pilot tube, and thermocouple.

Step 3: Set The Gas Control To “Pilot”

Push in and turn the gas control knob to the “Pilot” position. Some models require holding the knob down to allow gas flow to the pilot while lighting.

Step 4: Light The Pilot

While holding the gas control knob in, use a long-reach lighter or match to ignite the pilot. Hold the control knob for 20–30 seconds after the pilot lights to heat the thermocouple so it senses flame and allows gas flow to continue.

Step 5: Release And Turn To “On”

After holding the knob for the required time, slowly release it. If the pilot stays lit, turn the gas control knob from “Pilot” to “On” and replace the access panel. If the pilot goes out, repeat the sequence once or twice; persistent failure indicates a problem needing repair.

Relighting Furnaces With Electronic Ignition

Electronic ignition systems typically do not have a manual pilot. They use a spark igniter or hot surface ignitor to light the burners. Troubleshooting involves resetting power or checking the igniter rather than relighting a pilot.

Reset Procedure

Turn the thermostat to “Off” and the furnace power switch to “Off” or switch off the circuit breaker for 30 seconds. Restore power and set the thermostat to call for heat. The control board should initiate the ignition sequence.

When Electronic Ignition Fails To Light

Common causes include a failed igniter, faulty flame sensor, dirty burners, or control board issues. Do not attempt to light the main burner with a match. These systems are designed to be lit electrically; manual lighting can be unsafe and ineffective.

Troubleshooting Common Relighting Problems

Pilot Won’t Stay Lit

If the pilot lights but goes out when the knob is released, the thermocouple may be weak or misaligned, or the pilot flame may be too small due to dirt or draft. Cleaning and repositioning the pilot and replacing the thermocouple often resolves the issue.

Pilot Is Weak Or Yellow

A strong pilot flame should be blue with a small inner cone. A weak or yellow flame indicates debris, bad gas pressure, or improper air mixing. Cleaning the pilot orifice and verifying proper ventilation can help. Persistent discolored flames require professional inspection.

Repeated Pilot Outages

Frequent outages can signal a failing thermocouple, a draft blowing out the pilot, or an obstructed pilot assembly. Check for gaps around the furnace access panel, nearby exhaust fans causing drafts, or excessive dust buildup.

Smell Of Gas During Relight

Any gas odor requires immediate cessation of relight efforts. Ventilate, leave the area, and contact the gas provider. Trying to relight with an active gas leak can cause an explosion.

Maintenance Tips To Prevent Pilot Light Problems

• Inspect and clean the pilot assembly annually; remove dust and spider webs that can block gas flow.
• Replace the thermocouple every 3–5 years or at the first sign of instability.
• Ensure adequate combustion air and seal drafts around the furnace cabinet.
• Schedule professional furnace tune-ups each heating season.

When To Call A Professional

Call a licensed HVAC technician if there is a persistent inability to keep the pilot lit, frequent cycling, a defective gas control valve, broken thermocouple replacement needs, or any time a gas odor is present.

Complex issues such as gas pressure adjustments, control board failures, or replacement of ignition assemblies should be handled by a certified technician. Working on gas lines and combustion systems without proper training is hazardous and may violate local codes.

Replacement Parts And Costs

Common replacement parts include thermocouples, pilot orifices, gas valves, and igniters. Costs vary widely: thermocouples are relatively inexpensive for parts, but professional labor can increase total expense.

Part	Estimated Parts Cost	Notes
Thermocouple	$10–$60	DIY possible if comfortable with basic tasks
Pilot Orifice Cleaning/Replacement	$0–$50	Cleaning often resolves issues
Gas Control Valve	$100–$400	Professional replacement recommended
Electronic Igniter	$50–$300	Costs depend on type and model

Common Safety Codes And Best Practices

Furnace installations and repairs must comply with local building and fuel codes. For U.S. homeowners, the National Fuel Gas Code (NFPA 54) provides guidance on safe operation. Permits and licensed professionals are often required for gas line work.

Always follow manufacturer instructions, maintain proper clearances for combustion air, and ensure that venting systems are intact and unobstructed. Carbon monoxide detectors should be installed near sleeping areas and tested regularly.

Frequently Asked Questions

How Often Should The Pilot Be Relit?

Ideally, relighting should be rare. Regular maintenance minimizes outages. If relighting happens frequently, diagnose the root cause instead of repeatedly relighting.

Can A Homeowner Replace A Thermocouple?

A homeowner with mechanical aptitude can replace a thermocouple, but it involves shutting off gas, disconnecting fittings, and ensuring proper alignment. If uncertain, hire a qualified technician.

Is It Safe To Use A Candle Or Match To Relight?

Long-reach lighters are recommended to keep hands clear of burners. Short matches or candles increase burn risk and should be avoided. Never use open flame if a gas odor is present.

Why Does The Pilot Light Go Out After Relighting?

Common reasons include weak thermocouple, draft, dirty pilot orifice, or gas pressure problems. If relighting fails repeatedly, seek professional service.

Key Takeaways And Safety Reminders

Do not relight if there is an active smell of gas; evacuate and call professionals. Standing pilot relights are straightforward when done per manufacturer instructions and safety steps. Electronic ignition systems require electrical troubleshooting rather than manual lighting.

Regular maintenance, timely part replacement, and professional inspections reduce the likelihood of pilot light issues and keep the heating system operating efficiently and safely.