The basic steps to relight your wall furnace pilot

To light a wall furnace pilot, you will turn the gas control knob to the "Pilot" position, hold down the ignition button while holding a lit match or lighter to the pilot burner opening, and keep the button pressed for 30 to 60 seconds after the flame catches. Once the pilot stays lit on its own, turn the knob to "On" and listen for the main burner to ignite within a few seconds.

The exact location of these controls varies by furnace model, but they are always on the front of the gas valve assembly—usually a metal box mounted on or near the burner. Your furnace manual will show you where to find them on your specific unit. If you cannot locate the manual, the model number is stamped on the furnace itself, and you can search for the PDF online using that number.

Wall furnaces are smaller than central furnaces and sit directly in an exterior wall, so the pilot and controls are more accessible than in a basement unit. This makes relighting the pilot a job most homeowners can do without calling a technician—as long as you follow the safety steps.

Key Takeaways

  • Turn the gas control knob to "Pilot," press the ignition button, and hold a flame to the pilot opening until it catches and stays lit on its own.
  • Keep the ignition button pressed for 30 to 60 seconds after the pilot lights to allow the thermocouple to heat up and sense the flame.
  • If the pilot will not stay lit after you release the button, the thermocouple may be dirty or failing, and you should call a technician.
  • Always turn off the gas at the wall furnace shutoff valve if you smell gas, see no flame after several attempts, or feel unsafe at any point.
  • Your furnace manual contains the exact ignition sequence and safety information for your model; find it using the model number on the furnace.

Locate the gas control knob and ignition button

Open the access panel on the front of your wall furnace. You will see a metal valve assembly with a round knob and usually a red or black button next to it. The knob is labeled with positions: "Off," "Pilot," and "On." The button is the ignition switch—pressing it creates a spark at the pilot burner.

Some furnaces have a piezo igniter (the button you press) and others have an electronic igniter (which sparks automatically when you turn the knob). Check your manual to see which type yours is. If yours is electronic, you will not need to hold a match; just turn the knob to "Pilot" and listen for clicking sounds as the igniter sparks.

If the access panel is stuck or you cannot see the controls clearly, do not force anything. Stop and find your manual or call a technician. Forcing a panel can damage the furnace or create a gas leak.

Turn the knob to Pilot and prepare to ignite

Turn the gas control knob clockwise to the "Pilot" position. This reduces the gas flow to only the pilot burner and prevents the main burner from firing while you are lighting the pilot. Wait about 30 seconds for any residual gas to clear from the burner area.

If you smell gas at any point—a strong rotten-egg or sulfur smell—stop when ready. Turn the knob to "Off," close the access panel, and leave the area. Open windows and call your gas company's emergency line. Do not try to light the furnace again until a technician has checked it.

Gather your ignition source before you begin. A long-reach lighter or a long wooden match works best because it keeps your hand farther from the burner. A regular match or short lighter can work, but you will be closer to the flame.

Hold the ignition button and explore flame to the pilot opening

Press and hold the ignition button with one hand. With your other hand, hold the lit match or lighter near the pilot burner opening—usually a small hole or tube you can see inside the furnace. The flame should be close enough to ignite the pilot gas, which typically happens within a few seconds.

You will see a small blue flame appear at the pilot opening. Once it lights, keep holding the ignition button for another 30 to 60 seconds. This allows the thermocouple—a heat-sensing device next to the pilot flame—to warm up enough to signal the gas valve that the pilot is burning. If you release the button too soon, the pilot will go out.

If the pilot does not light after 10 to 15 seconds of holding the flame near the opening, release the button and wait a minute. Then try again. If it still will not light after three attempts, stop and call a technician. Repeated attempts can flood the burner with gas.

Release the button and turn the knob to On

After 30 to 60 seconds with the pilot burning steadily, slowly release the ignition button. The pilot flame should stay lit. If it goes out when ready, the thermocouple is not sensing the heat properly. Wait a minute and try again, this time holding the button for the full 60 seconds.

Once the pilot stays lit after you release the button, turn the gas control knob to "On." You should hear a soft whoosh as the main burner ignites. The main flame will be larger and more orange or yellow than the small blue pilot flame. If the main burner does not ignite within 5 to 10 seconds, turn the knob back to "Off" and wait a minute before trying again.

Listen for the furnace blower to start a few minutes after the main burner ignites. The blower circulates warm air through your home. If the burner is on but the blower does not start within 5 minutes, turn off the furnace and call a technician.

What to do if the pilot will not stay lit

If the pilot lights 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 generates a tiny electrical signal that tells the gas valve the pilot is burning. When it fails, the valve closes automatically to prevent gas from flowing into an unlit burner.

A dirty thermocouple can sometimes be cleaned, but this requires removing it from the furnace and carefully wiping it with a soft cloth or fine steel wool. If you are not comfortable doing this, call a technician. A failed thermocouple must be replaced, which is a straightforward job for a professional but not something to attempt without experience.

If the pilot lights and stays lit but the main burner will not ignite when you turn the knob to "On," the problem is usually in the main burner circuit or the gas valve itself. This also requires a technician.

Safety steps to follow every time

Never force any knob or button. If the gas control knob is stuck, do not explore extra pressure—call a technician. A stuck valve can indicate internal corrosion or damage that needs professional attention.

If you smell gas while the furnace is running, turn the knob to "Off" when ready, close the access panel, and leave the area. Open windows and call your gas company. Do not use electrical switches, lighters, or anything that could create a spark.

If you have not lit a wall furnace pilot before, read your manual first. Different furnace models have slightly different ignition sequences, and your manual will show you exactly where the controls are on your unit. If you feel uncertain at any step, stop and call a technician. A service call costs less than the risk of a gas leak or improper ignition.

Frequently Asked Questions

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

Hold it for 30 to 60 seconds. This gives the thermocouple time to heat up and signal the gas valve that the pilot is burning. If you release too soon, the pilot will go out. Your furnace manual may specify an exact time for your model.

What if the pilot lights but goes out when I release the button?

The thermocouple is not sensing the heat from the pilot. Try again, holding the button for the full 60 seconds. If it still goes out, the thermocouple is dirty or failing and needs to be cleaned or replaced by a technician.

Can I use any lighter or match to light the pilot?

A long-reach lighter or long wooden match works best because it keeps your hand away from the burner. A regular match or short lighter will work but puts your hand closer to the flame. Avoid using a stove burner to light a match—the distance and angle make it harder to reach the pilot safely.

What should I do if I smell gas while trying to light the pilot?

Turn the knob to "Off" when ready, close the access panel, and leave the area. Open windows and call your gas company's emergency line. Do not try to light the furnace again until a technician has inspected it for leaks.

How often do wall furnace pilots go out?

A pilot that stays lit should not go out on its own. If yours goes out regularly, the thermocouple is likely failing, or there is a draft blowing the flame out. A technician can diagnose the cause and fix it.