The basic steps to relight your furnace

To relight a propane furnace pilot light, turn the gas control knob to OFF, wait five minutes, then switch it to PILOT. Hold a lit match or lighter near the pilot burner opening while pressing and holding the ignition button (or knob, depending on your model) for 30 to 60 seconds. Once the pilot flame appears, keep holding the button for another 30 seconds to let the thermocouple heat up. Release the button, turn the knob to ON, and listen for the main burner to ignite within a minute.

The entire process usually takes less than two minutes once you have a light source ready. If the pilot does not stay lit after you release the button, wait five minutes and try again — the thermocouple may need more time to warm. If it fails a second time, the thermocouple itself may be faulty and need replacement by a technician.

Key Takeaways

  • Always turn the gas control knob to OFF and wait five minutes before attempting to relight the pilot, to clear any gas buildup.
  • The ignition button must be held down continuously while you light the pilot and for 30 seconds after the flame appears.
  • If the pilot light goes out when ready after you release the button, the thermocouple is not heating properly and may need professional replacement.
  • Once the pilot is lit and holding steady, turn the knob to ON and the main burner should ignite within one minute.

Where to find the pilot light and gas control on your furnace

The pilot light assembly is usually located at the bottom front of your furnace, behind a small access panel or door. You will see a small metal tube (the pilot burner) and a knob labeled with OFF, PILOT, and ON. Some furnaces have a red ignition button next to the knob; others have a button built into the knob itself that you press inward.

Before you open any panels, locate your furnace's main gas shut-off valve — it looks like a lever handle on the gas line coming into the furnace. You do not need to use it for a straightforward pilot relight, but you should know where it is in case you smell gas or need to stop the flow quickly. If you cannot find the pilot assembly or gas control knob, check your furnace manual or the manufacturer's website for your specific model number.

Safety checks before you start

Smell the air around your furnace. If you detect a strong rotten-egg or sulfur odor, do not attempt to light the pilot. This smell means gas is leaking. Leave the area, open windows, and call your gas company's emergency line or your propane supplier when ready. Do not use matches, lighters, or any ignition source.

Check that the area around the furnace is clear of clutter, dust, or anything flammable. Make sure you have a working lighter or long matches within arm's reach before you begin — you do not want to be fumbling for a light source while holding the ignition button. If you have a furnace with electronic ignition (a spark or hot surface igniter instead of a pilot light), do not attempt this procedure; electronic systems relight automatically and do not require manual lighting.

What to do if the pilot will not stay lit

If the pilot flame goes out within seconds of releasing the ignition button, the thermocouple is likely the problem. The thermocouple is a small metal rod that sits in the pilot flame and generates the electrical signal that tells the gas valve to stay open. When it fails, the valve closes automatically as a safety measure. Relighting will not fix a faulty thermocouple — it will straightforward go out again.

A thermocouple replacement costs between $150 and $300 including labor, depending on your furnace model and your technician's rates. Before you call for service, try cleaning the pilot burner opening with a thin wire or needle to remove any dust or debris that might be blocking the flame. Sometimes a weak or misaligned flame cannot heat the thermocouple enough to keep it working. If cleaning does not help, contact a licensed HVAC technician.

Troubleshooting a pilot that will not light at all

If you see no flame at all after holding the ignition button for 60 seconds, first check that gas is actually reaching the pilot. Turn the knob back to OFF, wait five minutes, and try again — sometimes the first attempt clears an air pocket in the line. If it still does not light, smell near the pilot burner opening. A faint rotten-egg smell means gas is flowing but not igniting.

When gas flows but will not light, the problem is usually a faulty ignition system or a pilot burner clogged with debris. Try gently blowing compressed air (from a can or compressor) into the pilot burner opening to clear any blockage. If you have no compressed air, a thin wire or needle can sometimes dislodge buildup. If the pilot still will not light after cleaning, or if you smell no gas at all at the burner, you need a technician to inspect the ignition components or check the gas line.

When to call a professional instead

Do not attempt to relight the pilot if you smell gas throughout your home, if you see visible damage to the furnace or gas line, or if you are uncomfortable working with gas appliances. Call your propane supplier or a licensed HVAC technician. If the pilot has gone out more than once in a short period, or if it goes out during normal operation, have a technician inspect the furnace before you try to relight it again — repeated outages often signal a deeper problem.

If your furnace is more than 15 years old and the pilot keeps failing, replacement of the entire furnace may be more cost-effective than repeated repairs. A technician can assess whether your furnace is worth fixing or whether a new unit would save you money over time.

Frequently Asked Questions

How long should I hold the ignition button?

Hold it for 30 to 60 seconds while the pilot is lit, then continue holding for another 30 seconds after the flame appears. This gives the thermocouple time to heat up and signal the gas valve to stay open. If you release too early, the valve will close and the pilot will go out.

What if I cannot get a flame to appear even with a lighter right at the burner?

Gas may not be reaching the pilot. Turn the knob to OFF, wait five minutes, and try once more. If still no flame, check that the main gas shut-off valve on the line into your furnace is fully open (the handle should be parallel to the pipe). If it is open and you still see no flame, the ignition system or gas line needs professional inspection.

Is it normal for the pilot light to go out sometimes?

An occasional outage from a power surge or strong draft is not unusual, but repeated outages within days or weeks signal a problem. A faulty thermocouple, a clogged burner, or a failing gas valve are the most common causes. Have a technician check the furnace if the pilot goes out more than once.

Can I light the pilot with the furnace door closed?

No. You need access to the pilot burner opening and the ignition button. Open the access panel or door fully and make sure you can see the burner clearly before you attempt to light it.

What does it mean if the main burner does not ignite after the pilot is lit?

The thermostat may not be calling for heat, or the main gas valve may not be opening. Check that your thermostat is set to HEAT and the temperature setting is higher than the current room temperature. If the thermostat is set correctly and the main burner still does not ignite, the main gas valve may be faulty and needs professional service.