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

Is your home feeling a little too chilly? A furnace with a pilot light that’s gone out is a common culprit, especially during the colder months. While modern furnaces offer electronic ignition, many older, reliable models still rely on a pilot light to ignite the main burner. A blown-out pilot light not only means no heat, but it also prevents your furnace from working, leaving you shivering and potentially vulnerable to frozen pipes.

Knowing how to safely relight your pilot light is a valuable skill for any homeowner. It can save you a costly service call, get your heat back on quickly, and give you peace of mind knowing you can handle this common household issue. It’s crucial, however, to prioritize safety and understand the steps involved before attempting to relight any pilot light. Following the correct procedure ensures you avoid potential gas leaks or other hazards.

What safety precautions should I take, and what are the exact steps for relighting my furnace’s pilot light?

How do I safely locate the pilot light assembly?

The pilot light assembly is typically located inside the furnace’s combustion chamber, behind a panel that is usually removable or hinged. Look for a small opening or viewing window that allows you to see the pilot light area without removing the panel entirely. The gas valve will usually be nearby, with labels indicating pilot light functions.

Finding the pilot light assembly safely requires taking precautions. First, always turn off the furnace’s power at the breaker box to prevent accidental electrical shocks. Second, shut off the gas supply to the furnace using the gas shut-off valve, which is usually a yellow handle on the gas pipe leading directly to the furnace. This is crucial to prevent gas leaks while you are working. Only after these steps should you carefully examine the furnace for the access panel. The panel may be held in place by screws, clips, or latches.

Once you locate the panel, carefully remove it. You might need a screwdriver or other tool. If you can’t find the pilot light assembly or are unsure how to proceed, consult your furnace’s manual or call a qualified HVAC technician. Don’t force anything or take chances with gas lines if you are not comfortable. Inside the combustion chamber, look for a small burner assembly with a thin tube (the gas supply line) connected to it and a thermocouple or flame sensor nearby. This is typically where the pilot light should be burning.

What if the pilot light won’t stay lit after holding the button?

If the pilot light won’t stay lit after holding the button down for the recommended time (usually 20-30 seconds), it indicates a problem with the thermocouple or flame sensor, a blocked pilot light orifice, or a gas supply issue. The thermocouple is a safety device that senses the pilot flame and allows the main gas valve to open. If it’s faulty, it won’t send the signal, and the gas will shut off, extinguishing the pilot.

The most common culprit is a malfunctioning thermocouple. Over time, these devices can corrode, weaken, or become dirty, preventing them from generating sufficient voltage to keep the gas valve open. Before replacing the thermocouple, try cleaning it gently with fine steel wool or sandpaper to remove any soot or debris. Ensure the thermocouple is properly positioned in the pilot flame; it should be directly enveloped by the flame’s tip. If cleaning doesn’t work, replacement is usually the best option. Thermocouples are relatively inexpensive and easy to install with basic tools. Another potential issue is a blocked pilot light orifice. A tiny amount of debris can obstruct the gas flow to the pilot, causing it to be too weak to properly heat the thermocouple. You can try cleaning the orifice with a small wire or a specialized pilot light cleaning tool. Be extremely careful not to enlarge the orifice, as this can affect the gas pressure and create a safety hazard. Finally, rule out a more general gas supply issue, such as a shut-off valve that isn’t fully open or a problem with the gas regulator. If you suspect a gas supply problem beyond a simple valve issue, contact a qualified gas technician immediately.

Where is the gas shut-off valve for my furnace?

The gas shut-off valve for your furnace is typically located on the gas supply pipe that feeds directly into the furnace. It’s usually a yellow or red handle, either a lever or a knob, situated close to where the gas pipe connects to the furnace itself.

The valve’s purpose is to quickly and safely cut off the gas supply to the furnace in case of emergencies or when performing maintenance. Knowing its location is crucial for safety. Always familiarize yourself with it before attempting any troubleshooting or maintenance on your furnace. If you’re unsure, consult your furnace’s manual or contact a qualified HVAC technician. In some instances, there might be a secondary gas shut-off valve located upstream from the furnace, often near the gas meter or where the gas line enters your home. While you’ll primarily use the valve directly on the furnace for service, knowing the location of the main shut-off can be beneficial in more severe situations. Remember, safety is paramount when dealing with gas appliances. If you suspect a gas leak, evacuate the premises immediately and call your gas company or emergency services from a safe location.

How long should I wait before relighting after a failed attempt?

It’s crucial to wait at least 5 minutes, and ideally 10 minutes, after a failed attempt to light your furnace pilot light before trying again. This waiting period allows any accumulated gas to dissipate, reducing the risk of a potentially dangerous explosion.

After a failed ignition, unburned gas can build up inside the furnace. Gas, by its nature, is highly flammable. If you attempt to relight the pilot light immediately, the concentration of gas might be too high, leading to a sudden and forceful ignition, potentially causing damage to the furnace or, more importantly, injury to yourself. The recommended waiting time is a safety precaution to allow the gas to naturally vent out of the system. Waiting longer than the minimum recommended time is always preferable to potentially dangerous consequences. Ensure there’s adequate ventilation in the area around the furnace during this period, perhaps by opening a window or door. If, after several attempts and appropriate waiting periods, the pilot light still won’t ignite, it’s best to contact a qualified HVAC technician to diagnose and resolve the underlying issue safely. Continuing to attempt relighting when there may be a larger problem can be hazardous.

What does the furnace smell like if there’s a gas leak?

If there’s a gas leak in your furnace, it will typically smell like rotten eggs or sulfur. This distinct odor is intentionally added to natural gas by utility companies because natural gas itself is odorless, making it difficult to detect leaks without an added scent.

The characteristic rotten egg smell is from a chemical called mercaptan, which is added to the gas to alert people to its presence. The concentration of mercaptan is carefully controlled to ensure that even a small leak can be easily detected. However, it’s important to note that in some rare cases, individuals might have difficulty smelling this additive, or the odor may fade over time due to soil conditions or other factors if the leak is underground before entering the home. Therefore, if you suspect a gas leak based on the smell, or if you experience symptoms like dizziness, nausea, or headache, it’s crucial to take immediate action. Do not attempt to locate the leak yourself. Immediately evacuate the building, leaving doors and windows open if possible. From a safe location away from the building, call your local gas company or 911 to report the potential gas leak and let trained professionals handle the situation.

How do I know if the thermocouple is faulty?

A faulty thermocouple is the most common reason a pilot light won’t stay lit after you release the pilot button. The primary symptom is that the pilot light ignites when you hold down the pilot button, but extinguishes as soon as you release it. This happens because the thermocouple isn’t generating enough millivolts to keep the gas valve open after you manually prime it.

When the pilot light flame heats the thermocouple, it generates a small electrical current (measured in millivolts). This current signals to the gas valve to remain open, allowing gas to continue flowing to the pilot light even after you release the pilot button. If the thermocouple is damaged, corroded, or simply worn out, it won’t produce sufficient voltage. This causes the gas valve to close as soon as you stop manually holding it open, effectively extinguishing the pilot. Sometimes, even a slightly weak thermocouple will result in an intermittent pilot light, where it stays lit for a short time but eventually dies out. Beyond the pilot light extinguishing, there are other potential indicators, although these are less definitive. You may notice visible corrosion on the thermocouple itself. Also, you can use a multimeter to test the thermocouple’s output. A healthy thermocouple should produce a reading within a specified range (usually around 25-30 millivolts when heated by the pilot flame); a significantly lower reading strongly suggests a faulty thermocouple. Replacing the thermocouple is a relatively inexpensive and straightforward repair, making it a good starting point when troubleshooting a pilot light issue.

Can a dirty burner cause the pilot light to go out?

Yes, a dirty burner can absolutely cause the pilot light to go out. A buildup of dust, dirt, rust, or debris on or around the burner assembly can interfere with the proper flow of gas to the pilot light and the proper mixture of gas and air needed for stable combustion. This can result in a weak, flickering, or inconsistent pilot flame, ultimately leading to it extinguishing.

A dirty burner disrupts the delicate balance required for the pilot light to function reliably. The pilot light relies on a consistent stream of gas and sufficient oxygen to maintain a stable flame. When the burner is clogged, it can restrict the gas flow, leading to a weak or sputtering flame that is easily extinguished by drafts or minor fluctuations in gas pressure. Furthermore, debris can partially block the air intake, causing an improper air-to-fuel ratio, resulting in incomplete combustion and a sooty flame that is prone to going out. Regular furnace maintenance, including cleaning the burner assembly, is crucial to prevent this issue. This can involve carefully brushing or vacuuming away any visible debris. In some cases, a professional HVAC technician may need to disassemble and thoroughly clean the burner components. Preventing dust and dirt buildup around the furnace area can also contribute to a cleaner burner and a more reliable pilot light.

And there you have it! Hopefully, your furnace is humming along nicely now, keeping you warm and cozy. Thanks so much for taking the time to read through these steps. We really appreciate it. If you have any other household hiccups, or just want to learn something new, come on back and visit us again soon. We’re always adding new guides and tips!