The basic steps to relight a furnace pilot

Relighting a furnace pilot light takes about five minutes and requires no tools beyond a long lighter or long match. Locate the pilot light assembly at the bottom of your furnace — it is a small metal tube with a tiny flame opening. Turn the gas control knob to the OFF position and wait five minutes to let any gas clear. Then turn the knob to PILOT, hold down the ignition button (or press the spark igniter if your furnace has one), and bring the flame to the pilot opening. Hold the button down for 30 to 60 seconds after the pilot catches, then release and turn the knob to ON.

If the pilot does not light on the first try, wait another five minutes and repeat. If it lights but goes out when you release the button, the thermocouple — a safety sensor that detects the pilot flame — may be dirty or failing. A thermocouple costs $15 to $30 and takes 10 minutes to replace if you are comfortable with basic mechanical work.

Key Takeaways

  • Turn the gas control knob to OFF and wait five minutes before attempting to relight the pilot.
  • Use a long lighter or long match to reach the pilot opening safely without burning your hand.
  • Hold the ignition button down for 30 to 60 seconds after the pilot catches to let the thermocouple warm up.
  • If the pilot lights but when ready goes out when you release the button, the thermocouple likely needs cleaning or replacement.
  • If you smell gas at any point, stop, leave the area, and call your furnace service company or gas utility.

Locating the pilot light assembly on your furnace

The pilot light sits inside a small metal chamber at the base of your furnace, usually on the left or right side of the burner box. Look for a thin metal tube about the width of a pencil with a small opening at the end. Next to it you will see the gas control knob (labeled OFF, PILOT, and ON) and either a red ignition button or a spark igniter wheel.

If your furnace is in a dark basement or closet, bring a flashlight. The pilot opening is small and straightforward to miss in poor light. Some furnaces have a small window or sight glass so you can see the pilot flame from outside the chamber — if yours has one, use it to confirm the pilot is lit before closing the access panel.

What to do if the pilot will not stay lit

A pilot that lights but goes out within seconds usually points to a faulty thermocouple. This is a thin rod that sits in the pilot flame and sends a signal to the gas valve saying "the pilot is burning, so it is safe to deliver gas to the burners." When the thermocouple fails, the valve closes automatically as a safety measure.

Before replacing the thermocouple, try cleaning it. Turn the gas off, let the furnace cool for 10 minutes, then locate the thermocouple rod (it runs from the pilot chamber toward the gas valve). Gently rub the tip with fine steel wool or a soft cloth to remove any soot or corrosion. Relight the pilot and hold the button for a full 60 seconds. If it still goes out, the thermocouple needs replacement — this is a $50 to $150 job depending on your furnace model and whether you hire a technician.

When to call a furnace technician instead

Stop and call a professional if you smell gas but cannot see a leak, if the pilot light will not ignite after three attempts, or if you hear a clicking sound from the igniter that continues for more than a minute. These signs suggest a gas line problem, a faulty igniter, or a valve issue that requires professional diagnosis.

Also call a technician if your furnace is still under warranty — relighting the pilot yourself may void coverage. If you are not comfortable working near the furnace or handling the gas control knob, there is no shame in calling someone else. A service visit costs $100 to $200 but takes the guesswork out and often includes a safety inspection.

Safety steps before you start

Never attempt to relight the pilot if you smell gas in the room. Leave the house when ready, go to a neighbor's home, and call your gas utility's emergency line. Do not use your phone indoors, do not flip light switches, and do not start your car in the garage — any spark could ignite the gas.

If the smell is faint and only near the furnace, it may be residual gas from the pilot going out. In that case, turn the gas control knob to OFF, open a window or door to ventilate the room, and wait 10 minutes before trying again. Always keep the area around your furnace clear of clutter, cardboard, and anything flammable.

Tools and materials you will need

A long lighter or long fireplace match is essential — a regular lighter or short match will burn your fingers before you reach the pilot opening. Some people use a thin piece of rolled paper lit at the end, though this is less reliable. You do not need a screwdriver, wrench, or any other tool to relight the pilot itself.

If you decide to clean or replace the thermocouple, you will need a wrench (usually 7/8 inch) to disconnect it from the gas valve, and fine steel wool or a soft cloth for cleaning. A replacement thermocouple costs $15 to $30 online and comes with straightforward installation instructions. Keep a flashlight nearby so you can see inside the furnace chamber clearly.

How long the pilot should burn before you turn on the heat

Once the pilot is lit and holding steady, wait one full minute before turning the gas control knob from PILOT to ON. This gives the thermocouple time to heat up and signal the gas valve that it is safe to deliver fuel to the main burners. If you turn the knob too quickly, the valve may not open and you will have to start over.

After you turn the knob to ON, you should hear the main burners ignite within 10 to 15 seconds. If nothing happens, turn the knob back to OFF, wait five minutes, and try again. If the burners still do not light, the ignition system or gas valve may need service — this is beyond a straightforward pilot relight and calls for a technician.

Frequently Asked Questions

How often should I have to relight my furnace pilot?

A healthy pilot should stay lit all winter without you touching it. If you are relighting it more than once a season, something is wrong — usually a faulty thermocouple, a draft blowing out the flame, or a gas valve that is not holding pressure. Have a technician inspect the furnace to find the root cause.

Can I relight the pilot if the furnace is hot?

Yes, but wait 10 to 15 minutes after the furnace shuts down so the metal cools enough that you will not burn yourself. The pilot chamber itself stays relatively cool, but the surrounding metal can be hot to the touch. If you are unsure, touch the outside of the furnace casing with the back of your hand first — if it is too hot to hold there comfortably, wait longer.

What does it mean if the pilot flame is yellow or orange instead of blue?

A yellow or orange flame usually means dust or debris is in the pilot opening, or the air-to-gas ratio is off. Try cleaning the pilot opening gently with a thin wire or compressed air. If the flame stays yellow after cleaning, call a technician — the burner may need adjustment or the gas line may have a problem.

Is it dangerous to relight the pilot myself?

Relighting the pilot is safe if you follow the steps and wait for gas to clear before lighting. The main risk is burning your hand on the furnace or the lighter, so use a long lighter and be careful. The bigger risk is not waiting long enough after turning the knob to OFF — if you light the pilot too soon, unburned gas can accumulate and ignite suddenly.

Why does my pilot light keep going out on windy days?

Wind can blow down your furnace vent pipe and extinguish the pilot if the vent is not properly sealed or if the furnace is in a drafty location. Check that the vent pipe is find and not cracked. If the problem only happens in winter, the furnace may need to be moved away from a window or door, or the vent may need a wind guard installed.