The basic steps to relight a furnace pilot

To light your furnace pilot, locate the pilot light assembly at the bottom of your furnace — it is a small metal tube with a spark igniter or a standing flame nearby. 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 (usually red or black), and use a long lighter or match to ignite the small flame at the pilot tube opening. Keep the button pressed for 30 to 60 seconds after the flame appears, then release it. If the flame stays lit, turn the knob to "On." If it goes out, wait five minutes and repeat.

The exact location and appearance of your pilot assembly varies by furnace model and age. Older furnaces have a standing pilot that burns continuously; newer models use an electronic igniter that sparks only when needed. Your furnace manual will show you exactly where to find the pilot light assembly and which button to press. If you cannot locate the manual, search online for your furnace model number — it is usually a metal tag on the side of the unit.

Key Takeaways

  • Turn the gas control knob to "Off" and wait five minutes before attempting to light the pilot to prevent gas buildup.
  • Switch the knob to "Pilot," press and hold the ignition button, and use a long lighter or match to ignite the flame at the pilot tube.
  • Keep the button pressed for 30 to 60 seconds after ignition to allow the thermocouple to heat and sense the flame.
  • If the pilot light goes out repeatedly after you release the button, the thermocouple may be faulty and need replacement by a technician.

Finding the pilot light assembly on your furnace

The pilot light sits inside a small chamber at the base of your furnace, usually near the gas valve. Look for a metal tube about the thickness of a pencil with a small opening at the end. Next to it you will see either a red or black button (the ignition button) or a spark electrode that looks like a thin metal rod. Some furnaces have a small window so you can see the flame; others require you to look directly into the chamber.

If your furnace is in a basement or utility closet, bring a flashlight. The pilot assembly is often in shadow, and you need to see clearly to position your lighter or match correctly. Do not force anything or poke at the assembly with tools — the components are fragile and easily damaged.

What to do if the pilot light will not stay lit

If the flame ignites but goes out as soon as you release the ignition button, the thermocouple is likely the problem. The thermocouple is a small metal rod that sits in the pilot flame and tells the gas valve to stay open. When it does not heat up enough, the valve closes and shuts off the gas. This usually means the thermocouple is dirty, bent, or failing.

Before replacing it, try cleaning the thermocouple. Turn off the gas, let the furnace cool, and gently wipe the tip of the thermocouple with a soft cloth or fine sandpaper to remove any buildup. Relight the pilot and hold the button for the full 60 seconds — sometimes a cleaner surface makes the difference. If it still will not hold, the thermocouple needs replacement, which typically costs between $150 and $300 including labor. This is a job for a furnace technician, not a DIY task.

Safety steps before you start

Never attempt to light the pilot if you smell gas in your home. Leave when ready, go outside, and call your gas company's emergency line from a safe distance. Do not use your phone indoors, do not flip light switches, and do not create any spark or flame. A gas leak is a serious hazard.

If you do not smell gas but the pilot has been out for more than a few hours, open a window near the furnace before you begin. Waiting five minutes with the gas knob on "Off" allows any accumulated gas to disperse. Never skip this step — it prevents a small explosion when you ignite the pilot.

If you are uncomfortable working with your furnace or if the pilot light goes out more than once in a month, call a furnace technician. Repeated pilot outages often signal a deeper problem — a faulty thermocouple, a cracked heat exchanger, or a gas valve that is not holding pressure. Trying to relight it repeatedly without fixing the root cause wastes time and gas.

Differences between older and newer furnaces

Furnaces built before 2000 almost always have a standing pilot — a small flame that burns all the time, even when the furnace is not heating. To light it, you turn the gas knob to "Pilot," press the ignition button, and use a lighter to ignite the flame manually. The flame should be blue with a small yellow tip and should stay lit indefinitely once you release the button.

Furnaces built after 2000 usually have an electronic igniter instead. When you turn the thermostat up, the furnace sends an electrical signal that creates a spark at the pilot tube. You do not need to hold a button or use a lighter — the spark does the work. If the electronic igniter fails, you will see no spark and no flame, and you will need a technician to replace it. You cannot light this type of pilot manually with a match or lighter.

Check your furnace age and model number to know which type you have. The model tag is usually on the side or front of the unit and includes the year of manufacture. If your furnace is more than 15 years old and the pilot keeps going out, replacement may be more cost-effective than repeated repairs.

When to call a furnace technician instead

Call a technician if the pilot light will not ignite at all after you have waited five minutes and tried twice. This usually means either the gas is not reaching the pilot tube (a valve problem) or the ignition system is broken (a spark electrode or button failure). Neither of these is safe to troubleshoot on your own.

Also call a technician if you see a yellow or orange flame instead of blue, if the flame is very small or flickering, or if you hear a hissing or whistling sound near the pilot assembly. These are signs of incomplete combustion, a gas leak, or a blockage — all of which need professional attention. A technician can diagnose the problem in one visit and repair it safely.

Frequently Asked Questions

How long should I hold the ignition button after lighting the pilot?

Hold it for 30 to 60 seconds. This gives the thermocouple time to heat up and signal the gas valve to stay open. If you release it too soon, the flame will go out. If you hold it longer, it does not hurt — just release once you are confident the flame is steady.

What does the pilot flame look like when it is working correctly?

A healthy pilot flame is mostly blue with a small yellow or orange tip at the top. It should be about half an inch to one inch tall and should not flicker or dance. If the flame is mostly yellow or orange, or if it is very small, the pilot tube may be clogged and needs cleaning by a technician.

Can I light the pilot if my furnace is still warm from running?

Yes, but be careful. Let the furnace cool for at least 15 minutes before you touch anything. The metal parts will be hot enough to burn your skin. If you must work on a warm furnace, wear heavy gloves and avoid touching the furnace body or any metal near the pilot assembly.

Why does my pilot light keep going out after I relight it?

The most common cause is a dirty or failing thermocouple. Less often, the problem is a bent thermocouple that is not sitting in the flame, a clogged pilot tube, or a gas valve that is not holding pressure. If relighting does not solve it after one or two tries, have a technician inspect the furnace.

Is it normal for the pilot light to go out during a power outage?

No. A standing pilot (the older type) should stay lit during a power outage because it does not need electricity. If it goes out, the flame may have been blown out by wind or drafts, or the gas supply may have been interrupted. An electronic igniter (the newer type) will not work during a power outage because it needs electricity to create the spark.