Why won't my gas fireplace pilot light stay lit?
Most of the time the pilot goes out because the safety sensor it heats, a thermocouple or thermopile, is weak, dirty or not sitting in the flame. A dirty pilot assembly, a draft across the pilot or low gas supply can cause the same thing. Replacing a thermocouple usually runs $150 to $350.
Chicago Chimney & Fireplace Repair · November 8, 2026
How a standing pilot keeps itself lit
Many gas fireplaces have a small pilot flame that burns all the time, or at least all season. That flame heats a sensor next to it. A thermocouple makes a tiny electric current when hot, and the gas valve stays open only while that current flows. Many fireplaces also have a thermopile, a larger version that powers the valve so a wall switch or remote can turn the main burner on.
When you hold the pilot button down, you are holding the valve open by hand. If the pilot goes out the moment you let go, the valve is not getting the signal it needs from the sensor.
The usual causes
These are the things worth checking, roughly in order:
- A pilot flame that is too small or lazy, often from dust or spider webs in the pilot tube. A healthy pilot flame wraps the tip of the sensor.
- A thermocouple or thermopile that has worn out or is bent away from the flame.
- A draft blowing across the pilot, from a vent problem, a missing or loose glass seal, or strong wind at the outside termination.
- Low gas supply to the fireplace, for example a partly closed shutoff valve.
- A failing gas valve, which is less common but does happen on older units.
- On newer fireplaces without a standing pilot, an igniter or control module problem rather than a thermocouple.
What parts usually cost
Typical 2026 ranges for gas fireplace parts are an igniter at $90 to $150, a pilot assembly at $100 to $350, a thermocouple at $150 to $350, and a thermopile or gas valve at $150 to $300. Yearly gas fireplace service is priced at the free inspection.
Parts have to match the make and model. We read the rating plate, check the pilot and sensors, and give you a written price before replacing anything.
Snow, vents and carbon monoxide
Most gas fireplaces vent through a pipe in the wall or the roof. Nicor Gas warns that snow or ice over a gas vent can cause carbon monoxide to build up, and it recommends clearing vents gently by hand or with a broom, not a shovel. A blocked vent can also make a pilot flicker or go out.
Nicor also recommends having gas appliances inspected at least once a year. If your fireplace is in a bedroom in Chicago, the city requires a CO alarm inside that room.
When to stop and call the gas company
If you smell gas, do not try to relight anything. Leave the house, then call from outside: Peoples Gas at 866-556-6002 in Chicago, or Nicor Gas at 888-642-6748 in most suburbs. Do not flip switches or start a car on the way out.
If there is no gas smell and the pilot simply will not hold, turn the valve off and book a visit. We work Sunday to Friday in 3-hour arrival windows.
FAQ
More answers
Should I leave the pilot on all summer?
That depends on the fireplace and your preference. Some owners turn the pilot off for the summer to save gas. Relight it carefully following the instructions on the unit.
The pilot stays lit but the burner won't come on. Is that the same problem?
Often it is the thermopile, the switch or the wiring rather than the thermocouple. The same visit covers it.
Can I clean the pilot myself?
Light dust on the outside of the glass and log set is fine to clean. Anything inside the gas controls is best left for service.
Does a gas fireplace need yearly service?
NFPA 211 calls for yearly inspection of chimneys and vents, and Nicor recommends inspecting gas appliances at least once a year.
Keep reading
More from the blog
Where does Chicago require carbon monoxide alarms?Illinois requires a CO alarm within 15 feet of every bedroom. Chicago adds alarms inside bedrooms with a fireplace and next to every furnace, boiler and water heater.
Do you need a permit to rebuild a chimney in Chicago?Chicago's Express Permit covers in-kind chimney rebuilds written on the permit; small in-kind repairs up to 50 sq ft need none, except possibly in landmark districts.
What changes when your chimney is in a Chicago Landmark district?In a Chicago Landmark district the Historic Preservation Division reviews chimney permits. What that means for your chimney, plus Oak Park's own district rules.
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