Pilot light trouble is inconvenient for any household. For most homes, it means not having a hot water supply, and for houses with older furnaces, it will mean disrupted home heating. While pilot lights could get turned off once in a while, it is surely not normal for them to keep going out.
This article will discuss the possible reasons why a pilot light does not stay on for much longer, and the effective ways to fix it. But first, what is a pilot light, and what is it for?
You relight it, it burns for a few hours or days, and then it goes out again — leaving you in the cold and wondering what is wrong. While the pilot light may seem like a simple flame, the system that keeps it burning involves several components that must all function together. When any one of them fails, the pilot either will not stay lit or extinguishes itself intermittently. Understanding the most common causes and their solutions helps you decide whether this is something you can address or whether professional service is needed.
Standing pilot lights are found in older furnaces — most furnaces manufactured after the early 2000s use electronic ignition instead. If your furnace has a standing pilot, it is likely 20 or more years old, and the pilot light issue may be just one sign that the system is approaching end of life. That said, many of these furnaces can be repaired and continue to provide reliable service if the underlying issue is addressed.
What This Problem Means
A pilot light that will not stay lit means the safety system is detecting a condition it considers unsafe — usually the absence of a confirmed flame — and is shutting off the gas supply to prevent unburned gas from accumulating. This is actually the safety system working correctly. The question is why the pilot flame is going out in the first place, or why the safety system is failing to detect it when it is lit.
Common Causes
Dirty or faulty thermocouple. The thermocouple is a safety device that sits in the pilot flame. When heated by the flame, it generates a small electrical signal that tells the gas valve the pilot is lit and it is safe to keep the gas flowing. If the thermocouple is dirty, corroded, or has moved out of proper alignment with the flame, it cannot generate an adequate signal and the gas valve closes, extinguishing the pilot. A dirty thermocouple can sometimes be cleaned to restore function, but a failed thermocouple must be replaced.
Thermocouple positioning. The tip of the thermocouple must be positioned directly in the path of the pilot flame. If it has shifted — due to vibration, thermal expansion and contraction, or accidental contact — the flame may not heat it sufficiently. Repositioning the thermocouple so its tip is engulfed in the pilot flame can resolve the issue.
Weak pilot flame. A weak or small pilot flame may not generate enough heat on the thermocouple to keep the gas valve open. A weak flame is often caused by a partially clogged pilot orifice (the small opening where gas exits to form the pilot flame). The orifice can be cleaned by a technician to restore proper flame size.
Drafts. A strong draft near the furnace can blow out the pilot flame. Sources of drafts include nearby windows, doors, HVAC returns, or air leaks in the furnace room. Identifying and eliminating the draft source resolves the problem without any furnace repair.
Gas supply issues. Fluctuations in gas pressure can cause the pilot flame to become unstable and extinguish. If other gas appliances also show signs of inconsistent operation (flickering flames, irregular performance), the issue may be with the gas supply rather than the furnace.
Failed gas valve. The gas valve controls gas flow to both the pilot and the main burners. If the gas valve is failing, it may intermittently shut off gas to the pilot, causing it to go out. Gas valve replacement is a professional repair.
How to Relight the Pilot
Most furnaces have relighting instructions printed on a label on the furnace itself. The general process is: turn the gas control knob to “off” and wait five minutes for any residual gas to dissipate. Turn the knob to “pilot” and hold it in while pressing the igniter button (if equipped) or lighting the pilot with a long match or barbecue lighter. Continue holding the knob in the pilot position for 30 to 60 seconds after the flame is established — this heats the thermocouple enough to generate the signal to keep the gas valve open. Then release the knob and turn it to “on.”
If the pilot stays lit after you release the knob, the system is operating normally. If the pilot goes out immediately when you release the knob, the thermocouple is likely the issue.
When to Call an HVAC Professional
Call a professional if the pilot will not stay lit after multiple relighting attempts, if you smell gas, if the pilot flame is yellow or orange instead of blue, or if you are uncomfortable working near the gas components of the furnace. A technician can test the thermocouple, clean the pilot orifice, check the gas valve, and verify safe operation. If the furnace is very old, the technician can also evaluate whether continued repair makes financial sense versus exploring replacement options.
Annual professional maintenance includes pilot system inspection and thermocouple testing, which catches developing problems before they result in a cold house.
Preventing the Problem
Schedule annual furnace maintenance that includes thermocouple inspection and pilot system cleaning. Eliminate drafts near the furnace. Keep the area around the furnace clean and free of dust, which can clog the pilot orifice. Regular filter changes maintain proper airflow through the system and reduce dust that can affect pilot components.
Frequently Asked Questions
Is it dangerous if my pilot light goes out?
Modern gas valves automatically shut off the gas supply when the pilot goes out, preventing gas accumulation. However, if you smell gas at any time, leave the house and call your gas company. The safety system is reliable, but a failed gas valve (rare) could allow gas to flow without a flame.
How much does thermocouple replacement cost?
Thermocouple replacement typically costs $100 to $250 including the service call and part. It is one of the more affordable furnace repairs.
Should I upgrade from a pilot light to electronic ignition?
This typically is not possible without replacing the entire furnace. However, if the furnace is old enough to have a standing pilot light, it may be approaching or past the age where replacement makes more sense than continued repair. A technician can help you evaluate this decision.
Why is my pilot flame yellow instead of blue?
A healthy pilot flame is blue with a small yellow tip. A mostly yellow or orange flame indicates incomplete combustion, possibly caused by a clogged pilot orifice, insufficient air supply, or contamination. A yellow pilot flame should be evaluated by a professional, as it can produce carbon monoxide.
A pilot light that keeps going out has a specific, identifiable cause. Systematic troubleshooting — starting with the thermocouple and pilot flame — resolves the issue in most cases.
If despite doing all the step-by-step procedures in this article, the pilot light in your boiler, or if your heater is blowing cold air, or water heater still keeps on going out then give us a call at Reliable Standard Heating, Air, & Solar. We will be more than happy to assist you, and finally, put an end to your pilot light problems. Give us a call anytime, or schedule a visit using our online appointment platform. See you soon!