How to light a pilot light on a furnace?

First, find out which kind of furnace you have — the instructions are completely different.

• Standing pilot: a small flame burns continuously and relights the burners each cycle. If it’s out, you relight it manually. Covered below.
• Electronic ignition (hot surface igniter or intermittent pilot): there’s no continuous flame to relight. The furnace ignites itself electronically each time it calls for heat. If it’s not lighting, the cause is different — skip to Electronic Ignition Furnaces below.

If you’re not sure which you have, look through the access panel. A standing pilot furnace has a small, always-present flame near the burners (when working) and a gas valve with Off/Pilot/On positions. If you see no flame at all, even when the furnace is running normally, you likely have electronic ignition.

Lighting a Standing Pilot

Before you start: turn the furnace off, and make sure the area is ventilated. If you smell gas at any point, stop, leave the house, and call your gas utility — don’t attempt to light anything.

1. Remove the access panel to reach the gas valve and pilot assembly.
2. Turn the gas control knob to Off and wait about 5 minutes for any residual gas to clear.
3. Turn the gas control knob to Pilot.
4. Press the knob in and hold it down — this is the knob itself, not a separate button on most residential furnaces.
5. While holding it in, light the pilot with a long lighter or match, aiming at the pilot opening.
6. Keep holding the knob in for 30-60 seconds after the flame catches. This gives the thermocouple time to heat up and signal that it’s safe to keep the gas flowing. Release too early and it’ll go out.
7. Once it stays lit on its own, release the knob and turn it to On.

If it won’t stay lit after a couple of tries, don’t keep repeating the process — move to the troubleshooting section below.

Checking the Flame

• Blue and steady: normal, healthy combustion.
• Yellow, orange, or flickering: incomplete combustion, often from a dirty pilot assembly or a draft. Worth having checked even if it’s still technically working.
• Doesn’t fully engulf the thermocouple: the thermocouple won’t heat properly, and the pilot may keep going out even though it lit successfully.

Why the Pilot Won’t Stay Lit

A failing thermocouple is one of the most common reasons a pilot won’t hold — it’s an inexpensive part, but testing and replacing it safely is a technician job.

Electronic Ignition Furnaces {#electronic-ignition}

If your furnace uses electronic ignition, there’s no pilot to light manually — the system handles ignition itself every time it calls for heat, either with a hot surface igniter (a glowing element) or an electronic spark. If it’s not producing heat, the cause is almost always one of these instead:

• Hot surface igniter failed — these are fragile and wear out over time, similar to a light bulb. A technician can test and replace it.
• Flame sensor dirty or failing — the furnace may ignite briefly and then shut off because it can’t confirm the flame.
• Control board fault — less common, but can prevent the ignition sequence from starting at all.

None of these are something to troubleshoot by trying to manually “light” anything — there’s no pilot flame to light, and attempting to force one is not how these systems work. This is technician territory.

When to Call a Professional

• The pilot won’t stay lit after a couple of careful attempts
• You smell gas at any point — stop immediately and call your gas utility from outside
• You have electronic ignition and the furnace isn’t producing heat
• The flame is consistently yellow rather than blue
• You’re not comfortable working around the access panel of a gas appliance

Preventing Pilot Light Problems

• Schedule an annual furnace inspection, ideally before heating season
• Keep the area around the pilot assembly clean and free of dust
• Replace the furnace filter regularly — airflow issues can contribute to drafts near the pilot
• Address a flickering or yellow flame promptly rather than waiting for it to go out entirely

Common Questions

How do I light a furnace pilot light?

Turn the gas knob to Pilot, hold it in, light the flame, and hold for 30-60 seconds before releasing. Full steps above.

What if the pilot light won’t stay lit?

Most often a failing thermocouple or a draft. See the troubleshooting table above — if it keeps happening after a couple of tries, that’s a technician visit rather than something to keep repeating yourself.

Why is the pilot flame yellow instead of blue?

Incomplete combustion, usually from a dirty pilot assembly or insufficient combustion air. Worth having checked even if the furnace is otherwise working.

Where is the pilot light on a furnace?

Usually behind the lower access panel, near the burners. Look for the gas control valve with Off/Pilot/On positions nearby.

My furnace won’t light and I don’t see a pilot flame anywhere — is something wrong?

Possibly not with the pilot — you may have electronic ignition, which doesn’t use a standing pilot at all. See the electronic ignition section above.