To fix a gas fireplace that won't stay lit, the most common solution is to clean or replace the thermocouple (or thermopile)—the small metal probe in the pilot flame that signals the gas valve to stay open. Always turn off the gas and allow the unit to cool before inspecting.
Your gas fireplace could be turning off for several reasons. The most like culprits are likely tied to some kind of problem with your setup. Anything from issues with your pilot light, clogged ports on burners, damage to heating components, and thermocouple/thermopile malfunctions can be to blame.
Cleaning a gas fireplace thermocouple is a simple maintenance task that fixes pilot lights that won't stay lit. Turn off the gas and let the unit fully cool. Remove the glass and logs to access the pilot assembly. Gently scrub the thermocouple rod with high-grit sandpaper or emery cloth, wipe away debris, and reassemble.
A gas fireplace thermocouple replacement typically costs between $𝟏𝟐𝟎 and $𝟑𝟓𝟎 in total, depending on whether you do it yourself or hire a professional. The part itself is inexpensive, but professional labor rates make up the bulk of the final bill.
Gas fireplaces typically last between 10 to 20 years, though high-quality models that receive annual professional maintenance can last up to 30 years. The exact lifespan often depends on the specific components, as parts will degrade at different rates.
14 Common Gas Fireplace Problems & What to Do
Gas Fireplace: $3,500-6,500 (New construction), or $4,000-8,000 (remodel) Installing a gas fireplace either involves starting from scratch (new construction, addition, etc.), or removing an already existing fireplace and putting a new fireplace in its place.
Replacing a thermocouple is a relatively easy fix that can take less than two hours. This guide reviews how to replace a thermocouple to ensure gas appliances stay in good working order, as well as how to relight a pilot light.
A healthy pilot flame should be a crisp, steady blue, engulfing the top third of the thermocouple. A weak, yellow, or wavering flame often indicates a dirty pilot orifice or a gas supply issue, preventing the thermocouple from getting hot enough to function.
Replacing a thermocouple is something you can do at home, only requiring an open-end wrench and screwdriver or nut driver. Safety First: Before starting, turn off the power and gas supply to the furnace.
Steps for Furnace Thermocouple Cleaning
You will want to clean the thermocouple with a piece of emery cloth or high grit (1000) sandpaper. This may resolve the issue. Another issue that could be causing this is the connection point between the thermocouple lead and the gas valve.
Try Cleaning Off Your Thermocouple if Your Pilot Light Won't Stay Lit. It's not unusual for the thermocouple to collect carbon deposit buildup after a season of use. After all, your thermocouple is sitting in a direct flame the majority of the time.
Yes, unburned gas will leak if a pilot light goes out, but the danger level depends on the type of appliance and its safety features.
When a thermocouple won’t stay lit, it is usually because a dirty, misaligned, or faulty sensor is failing to detect the pilot flame, causing a safety valve to shut off the gas.
Over time, factors like mechanical damage, excessive heat, and contamination can cause thermocouples to fail. Knowing why thermocouples go bad and recognizing the signs of wear can help prevent inaccurate readings, extend their lifespan, and maintain optimal performance in your temperature monitoring systems.
The part is rather small and inexpensive, but replacing it requires the expertise of a professional plumber for safety reasons. Having a thermocouple replaced usually costs $125-200, while the part itself is about $15-25.
Thermocouple Lifespan
A thermocouple usually lasts 3-5 years on a regularly used standing-pilot system. Some last longer, but once they begin to weaken you'll see the classic symptom: the pilot won't stay lit unless you hold the knob.
However, like all appliances, a gas fireplace doesn't last forever. If you're considering upgrading your fireplace or need to replace your old one, it's important to weigh the safety, efficiency, and cost aspects of gas fireplace replacement.
It is usually cheaper to run a gas fireplace if you only want to heat a single room, because you aren't paying to push heat through the entire house. However, central heat is more fuel-efficient, making it cheaper if you need to warm your entire home.