How to Light Furnace Pilot: A Step-by-Step Guide

What safety precautions should I take before lighting a furnace pilot?

Before attempting to light a furnace pilot, the most critical safety precaution is to ensure there is no gas accumulation around the furnace. Thoroughly smell around the furnace area for any trace of gas odor. If you smell gas, immediately evacuate the building and contact your gas company or a qualified HVAC technician from a safe location. Do not attempt to light the pilot yourself.

Before proceeding, confirm that the gas supply valve leading to the furnace is in the “off” position. This valve is typically located on the gas pipe near the furnace. Ensure adequate ventilation by opening windows and doors in the area. This helps dissipate any residual gas that might be present. Also, familiarize yourself with the furnace’s specific instructions, usually found on a label affixed to the unit or in the owner’s manual. Different furnaces may have slightly different procedures, and following the manufacturer’s guidelines is crucial for safety and proper operation. Finally, ensure you have a long lighter or a lit taper readily available. Avoid using matches, as they can be difficult to handle in the confined space of the pilot light assembly and pose a burn risk. A long lighter or taper allows you to safely introduce a flame without placing your hand too close to the gas source. If, at any point during the lighting process, you smell gas again, immediately stop, turn off the gas supply valve, and ventilate the area before attempting to relight. If unsure, always call a qualified technician.

How do I identify the pilot light assembly on my furnace?

The pilot light assembly is usually located near the bottom of the furnace, within the burner compartment. Look for a small metal structure with a tiny opening where a flame would normally be visible. It will also have a thin metal tube (the gas supply line) connected to it and a thermocouple or thermopile nearby, which are small metal rods that sense the pilot flame.

To pinpoint the pilot light assembly, first locate the burner compartment access panel on your furnace. This is typically a removable panel at the bottom of the unit, often secured by screws or clips. Once you remove the panel, shine a flashlight inside. The pilot light assembly will be situated close to the main burners. It will be a small, distinct unit, separate from the larger burners, designed specifically to house and maintain a small, constant flame. Pay attention to the thin copper or aluminum gas line that feeds directly into this assembly; this is a key identifying feature.

If you are having difficulty locating it, consult your furnace’s owner’s manual. Most manuals include diagrams that clearly show the location of all the furnace components, including the pilot light assembly. If you don’t have a physical manual, you can often find a digital version by searching online for your furnace’s make and model number followed by “owner’s manual” or “installation guide.” Remember to always turn off the power to the furnace before attempting to locate or work on any of its components for safety.

Why does my furnace pilot light keep going out?

A pilot light that repeatedly goes out is usually caused by a lack of gas supply, a faulty thermocouple, a dirty pilot light assembly, or a draft. These issues prevent the pilot flame from staying lit consistently, which is crucial for the furnace to operate correctly.

The most common culprit is a malfunctioning thermocouple. The thermocouple is a safety device that senses the heat from the pilot flame. When the pilot is lit, the thermocouple generates a small electrical current. This current tells the gas valve to stay open, allowing gas to flow to the main burners when heat is called for. If the thermocouple is dirty, loose, or damaged, it won’t generate enough current, and the gas valve will shut off, extinguishing the pilot light. You can try cleaning the thermocouple with fine steel wool, but replacement is often the best solution. Another frequent cause is a dirty pilot light assembly. Over time, dust, debris, and spiderwebs can accumulate around the pilot orifice, partially blocking the gas flow. This restricted gas flow creates a weak or unstable pilot flame that is easily extinguished. A thorough cleaning of the pilot light assembly, including the orifice and surrounding area, is often necessary to restore a consistent and strong pilot flame. Also, ensure there are no drafts blowing directly on the pilot light, as even a slight breeze can be enough to extinguish it. Finally, ensure adequate gas pressure to the furnace. A problem within the gas line itself, or within a whole house gas supply issue, can cause fluctuations in gas pressure that starve the pilot light. If other gas appliances are experiencing similar problems, or if the above steps don’t work, it might be time to call in a professional HVAC technician to diagnose the underlying problem and ensure your furnace operates safely and efficiently.

How long should I hold the gas valve button down when lighting the pilot?

You should typically hold the gas valve button down for approximately 20-30 seconds after the pilot light ignites. This allows the thermocouple or thermopile to heat up sufficiently and generate enough electricity to keep the gas valve open and the pilot light lit once you release the button.

Holding the button down for the correct duration is crucial for the pilot light to stay lit consistently. The thermocouple (a small, metal safety device) generates a tiny electrical current when heated by the pilot flame. This current energizes the gas valve’s holding coil, keeping the valve open and supplying gas to the pilot light. If you release the button too soon, the thermocouple won’t be hot enough to maintain the electrical current, and the gas valve will close, extinguishing the pilot. If the pilot light fails to stay lit after repeated attempts of holding the button down for 20-30 seconds, there might be other issues, such as a faulty thermocouple, a dirty pilot orifice, or a problem with the gas supply. In such cases, it is best to consult a qualified HVAC technician to diagnose and repair the issue safely.

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

Immediately stop what you’re doing, turn off the gas supply to the furnace, and ventilate the area by opening windows and doors. Do not attempt to light anything or operate any electrical switches. Leave the area and call your gas company or a qualified HVAC technician from a safe location to inspect the system for leaks.

If you smell gas, it indicates a potentially dangerous gas leak. The most important thing is to prevent any source of ignition, which could cause an explosion or fire. Turning off the gas supply at the source (usually a valve near the furnace or at the gas meter) cuts off the flow of gas and helps to minimize the leak. Ventilating the area allows the accumulated gas to dissipate, further reducing the risk. Never try to find the source of the leak yourself. Gas leaks can be difficult to detect, and improper handling can make the situation worse. Professional technicians have specialized equipment to locate and repair leaks safely. The gas company will also check for gas levels in the surrounding area to make sure there is no continuing danger. It’s crucial to prioritize safety and let qualified professionals handle the issue.