Learn How to Relight Your Furnace Pilot Light

Understanding Your Furnace Pilot Light and When It Goes Out

A pilot light is a small, continuously burning flame inside your furnace that serves a critical purpose: it ignites the main burner when your heating system needs to produce warm air. Think of it as the starter for your furnace. The pilot light typically burns at around 1,000 to 1,200 degrees Fahrenheit, which is hot enough to trigger the ignition of the much larger main burner flame when the thermostat calls for heat.

Most furnaces manufactured before the year 2000 have pilot lights that remain lit at all times, even during warmer months when you are not using your heating system. Newer furnace models often feature electronic ignition systems instead, which means they do not rely on a constantly burning pilot light. If your furnace was installed recently, you may not have a pilot light at all. Checking your furnace manual or looking at the unit itself will tell you whether your system uses a traditional pilot light.

Several common reasons explain why a pilot light goes out. A sudden gust of wind, though rare indoors, can extinguish the flame. More commonly, the pilot light goes out due to a dirty or corroded thermocouple—a safety device that senses whether the pilot light is burning and signals the furnace to allow gas to flow. Dust accumulation on the pilot orifice, which is the small opening where gas flows to create the pilot flame, also causes frequent outages. In some cases, a bent or misaligned flame spreader, the component that directs the pilot flame, prevents proper ignition.

Practical takeaway: Before attempting to relight your pilot light, locate your furnace manual or the information label on your furnace unit itself. This documentation will provide specific instructions for your model and tell you whether your furnace actually has a pilot light.

Safety Considerations Before Attempting to Relight the Pilot Light

Safety must come first when working with any gas-burning appliance. Before you touch anything on your furnace, turn off the gas supply using the valve located on the gas line leading to the furnace. This valve typically looks like a small lever or knob. Turn it perpendicular to the direction of the gas line—this cuts off gas flow to the entire unit. Once you have done this, wait several minutes to allow any residual gas to dissipate from the furnace chamber.

Next, check the area around your furnace for any signs of a gas leak. Natural gas has an odor—described as similar to rotten eggs or sulfur—specifically added so people can detect leaks. If you smell gas, do not attempt to relight the pilot. Instead, leave your home immediately and call your gas company's emergency line from a location away from your house. Do not use your phone inside the house or flip any light switches, as these actions can create sparks.

Ensure the area around your furnace is clear and well-ventilated. Remove any items stored near the furnace, including boxes, rags, or cleaning supplies. Many furnace rooms lack windows, so opening a door to the room and running a fan pointed outward during the relighting process helps move air through the space. Wear long sleeves and use caution around any moving parts, such as the blower fan, though these should not be running when the furnace is off.

You will need specific tools and materials: a flashlight or headlamp to see inside the furnace chamber, a long-reach lighter or long matches, and a screwdriver if your furnace access panel requires removal. Never use a regular match held between your fingers—the distance from the match head to your hand is too short, risking a burn. Never use a cigarette lighter or stove flame to light the pilot; these methods are difficult to control and dangerous.

Practical takeaway: Write down your furnace model number and gas company phone number before you begin. Keep this information visible so you can quickly reach help if something goes wrong or if you smell gas at any point.

Locating the Pilot Light Assembly and Control Valve

Finding your pilot light is the first step after ensuring safety. Open the access panel on the front of your furnace, which typically requires removing one or two screws. Behind this panel, you will see the furnace's interior chamber. Use your flashlight to look for a small metal tube running along the bottom or side of the interior. This tube is the pilot burner assembly, and it looks like a small nozzle with a thin flame port.

Near the pilot burner assembly, you will find the control valve, which is the component that manages gas flow to the pilot light. This valve has settings marked on it. The markings typically show three positions: "OFF," "PILOT," and "ON." Some furnaces also display a small image or symbol showing how to position the valve. The valve itself is usually a knob or lever that you can turn by hand—no tools are required.

You will also see the thermocouple near the pilot burner. The thermocouple looks like a thin metal rod, often copper-colored, positioned to sit directly in or very close to the pilot flame. This component is crucial because when the pilot light flame touches it, the thermocouple heats up and generates a small electrical signal. This signal tells the furnace control board that the pilot is lit and that it is safe to release gas for the main burner.

Some furnaces have an ignition button or spark electrode nearby. Newer models with electronic ignition have a button labeled "IGNITE" or marked with a spark symbol. If your furnace has electronic ignition, you will press this button repeatedly while attempting to light the pilot. If you have an older manual-ignition model, you will simply hold a lighter to the pilot port while turning the control valve.

Take a moment to examine the inside of the furnace chamber with your flashlight. Look for any visible dirt, dust, or debris on the pilot assembly. If you see heavy buildup, a professional cleaning may help, but you can proceed with relighting first. Many pilot lights relight successfully even with minor dust accumulation.

Practical takeaway: Take a photo of your pilot assembly with your phone before beginning. This image will serve as a reference if you need to contact a technician or if you need to explain the situation to someone else.

Step-by-Step Process for Relighting the Pilot Light

Once you have located the pilot assembly and confirmed the gas is off, follow these precise steps to relight your pilot. First, turn the control valve to the "OFF" position and wait five full minutes. This waiting period is critical because it allows any residual gas inside the furnace chamber to disperse completely. Lighting the pilot without this wait could cause a small explosion or dangerous flash of fire inside the chamber.

After five minutes, turn the control valve to the "PILOT" position. Do not turn it all the way to "ON" yet. With the valve in the "PILOT" position, gas will flow only to the pilot burner, not to the main burner. Now, use your long-reach lighter or long matches to ignite the pilot flame. Position the flame near the end of the pilot burner nozzle—this is where the gas is coming out. You should see a small blue flame appear almost immediately. If you have an electronic ignition system, press the ignition button repeatedly while holding the lighter to the pilot port.

Once the pilot light is burning steadily with a blue flame, hold the control valve in the "PILOT" position for thirty seconds to one minute. During this time, keep the lighter near the flame to ensure it stays lit. If the flame goes out before this time has passed, repeat the waiting and lighting process. After thirty to sixty seconds, you can remove the lighter. The thermocouple should now be hot enough to maintain the pilot light.

Now comes the important test: while still holding the control valve in the "PILOT" position, slowly release your grip on the knob. The pilot flame should remain lit. If it stays lit, you have successfully relit the pilot. If it goes out when you release the valve, the thermocouple is not sending a proper signal, and the valve is shutting off the gas. In this case, wait five minutes and try again.

Once the pilot is holding its own, turn the control valve from "PILOT" to "ON." Your furnace should now begin operating normally. You will hear a slight whooshing sound as the main burner ignites, and warm air should start flowing through your vents within a minute or two. Check your thermostat to make sure it is set