My gas fireplace pilot won't stay lit — why?
Most of the time the pilot goes out because the thermocouple or thermopile isn't making enough voltage to hold the gas valve open, or because the pilot flame is weak from dust and lint in the pilot assembly. In the Valley, a summer of dust storms is often enough to do it. Cleaning or replacing the pilot parts usually runs $150 to $350.
Scottsdale Chimney Co. · October 4, 2026
How the pilot is supposed to work
A standing-pilot gas fireplace keeps a small flame burning against a thermocouple and a thermopile. Heat makes a tiny electrical current, and that current holds the gas valve open. If the flame is weak or the sensor is worn, the current drops and the valve shuts the gas off — which is a safety feature, not a fault.
The usual causes
- A dirty pilot assembly: dust, lint and spider webs make the flame small and yellow instead of a strong blue.
- A worn thermocouple or thermopile: they wear out with years of heat and are the most common part we replace.
- The pilot was off all summer and now needs to be relit and held long enough to heat the sensor.
- Low gas pressure or a gas valve that is failing.
- On electronic-ignition units: dead batteries in the receiver or a failed igniter.
What you can safely check
Read the lighting instructions on the plate inside the fireplace and follow them exactly, including how long to hold the knob in. Replace the remote and receiver batteries. Make sure the gas shut-off valve near the fireplace is fully open. If it still won't hold, stop there — don't take the valve apart or keep relighting it over and over.
Pilot on, but the burner won't light
If the pilot burns but the main flames never come on, the problem is usually the thermopile (which powers the switch or remote), the wall switch and its wiring, or the remote receiver. These are small parts and usually a same-visit repair.
FAQ
More answers
How much does it cost to fix a pilot that won't stay lit?
In Scottsdale, pilot, thermocouple or thermopile repairs usually run $150 to $350. An igniter or remote receiver is $200 to $450, and a gas valve or control board $400 to $1,200. The diagnostic visit is free.
Should I leave the pilot on all summer?
That's up to you. Turning it off saves a little gas and heat in the summer; leaving it on keeps moisture and spiders out of the pilot. Either way, have the fireplace serviced before the first cool night.
Keep reading
More from the blog
Do gas fireplaces need to be cleaned and serviced?Gas fireplaces burn clean but still need a yearly check. What a gas fireplace service includes, why Valley dust matters, and what it costs in Scottsdale.
Why is there a white film on my gas fireplace glass?Why the glass on a gas fireplace gets a cloudy white haze, how to clean it safely, and when the film or soot means something is wrong.
Why does my gas fireplace smell?A burning-dust smell on the first fire is normal. A rotten-egg smell is not. What each gas fireplace smell means in Scottsdale homes and who to call.
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