Lowes Chimney Sweep Blog
Why Does My Gas Fireplace Pilot Light Keep Going Out?
By the Lowes Chimney Sweep crew · Plano, TX
A pilot light that lights but will not stay lit is most often a worn thermocouple or thermopile, a dirty pilot assembly, or a draft blowing the flame off its sensor. All three are routine professional repairs. A pilot that will not light at all, or goes out with a gas smell, is a different and more urgent problem.
How the Pilot System Works
The pilot flame heats a small sensor — a thermocouple or thermopile — that generates a tiny electrical signal telling the gas valve "the flame is alive, keep the gas open." When that signal weakens for any reason, the valve does exactly what it was designed to do: it shuts the gas off. So a dying pilot is usually not a gas problem — it is a signal problem.
The Usual Causes, in Order
A worn thermocouple or thermopile. These sensors degrade with age and simply produce less signal until the valve stops trusting them. It is the single most common cause and an inexpensive part.
A dirty pilot assembly. Dust, pet hair, and spider webs — genuinely, spiders love pilot tubes — restrict the flame until it is small, yellow, and barely touching the sensor. A weak flame cannot heat the sensor properly.
Draft interference. If the pilot dies mainly on windy days or when the room pressure changes, a downdraft may be physically pushing the flame off the sensor.
A failing gas valve or loose connection. Less common, and a diagnosis for a technician with a millivolt meter — not a guess-and-replace part.
What You Can Safely Check
Look at the pilot flame while it is lit: a healthy pilot is steady and blue and wraps the sensor tip; a weak one is small, yellow, or dancing. Note the pattern — dies immediately after releasing the control knob (classic thermocouple), dies minutes later, or dies only in certain weather. That pattern is half the diagnosis. Relighting per the manufacturer's instructions is fine; going further — cleaning, bending, or replacing parts on a gas appliance — is not a homeowner job.
When to Stop and Call
Stop relighting and call a professional if the pilot dies more than occasionally, and stop using the unit entirely if you ever smell gas, hear hissing, or see soot forming on the glass or logs. A pilot that repeatedly fails is the system telling you a safety component is no longer reliable — resetting it over and over is ignoring the message.
How a Professional Fixes It
A gas fireplace technician tests the thermocouple or thermopile output with a meter — real numbers, not guesses — cleans the pilot assembly and orifice, checks the flame pattern against spec, and verifies the valve's response. Weak sensors get replaced on the spot; a properly cleaned and adjusted pilot should hold reliably for seasons. Our gas fireplace repair visits end with the whole ignition sequence tested repeatedly and photos of what was replaced.
The DFW Factor
Most DFW gas fireplaces sit unused from March to November — nine months for dust and insects to move into the pilot assembly. That is why "it worked fine last winter" pilots so often refuse to stay lit on the first cold week of November. Having the unit serviced in fall, before the first cold front, is the difference between a working fireplace on the first cold night and a service call during the rush.
Tired of relighting a pilot that will not stay lit? Tell us the pattern — when it dies and what the flame looks like — and request a Free Online Quote, or call (214) 225-8874. We will test the sensor with a meter and fix the actual cause, not just relight it.
Quick Answers
Is a pilot light that keeps going out dangerous?
The safety valve is doing its job by closing the gas, so the failure itself is usually safe. What is unsafe is repeatedly forcing a failing system to run — and any gas smell, hissing, or sooting means stop using the unit and call immediately.
How much does thermocouple or thermopile replacement cost?
It is one of the least expensive gas fireplace repairs — the part is modest and replacement is quick once diagnosed. The meter test tells us definitively whether the sensor is the problem before anything is replaced.
My pilot only goes out on windy days. Is that the same problem?
Probably not — that pattern points to a downdraft blowing the flame off the sensor rather than a bad part. That is a venting and cap question, which is exactly why we check flame behavior and draft together during diagnosis.
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