Symptoms
- Pilot lights but goes out once the button or knob is released
- Repeated attempts to relight don't help
- No heat because the main burner never gets a chance to ignite
Likely causes
- CommonDirty or misaligned thermocoupleThe sensor needs to sit directly in the pilot flame to keep the gas valve open.
- CommonWorn-out thermocoupleThese wear out over years of use and eventually can't hold the valve open even when clean.
- PossibleDraft from a nearby vent or door blowing out the flameA drafty room can extinguish a small pilot flame repeatedly.
- PossibleWeak pilot flame from a partially clogged orificeDust or debris can restrict gas flow enough to weaken the flame.
What to do
- Follow the printed lighting instructions, holding the pilot control in for the full specified time (often 30–60 seconds).
- Check that the pilot flame is a strong, steady blue, not small, yellow, or flickering.
- Confirm the thermocouple tip sits directly in the pilot flame; adjust gently if it's visibly off to the side.
- With the gas off and the assembly cool, clean the thermocouple tip with fine sandpaper if it looks dirty.
- Close nearby doors or windows to rule out a draft blowing the pilot out during your test.
- If cleaning doesn't help, the thermocouple likely needs replacement, which is a straightforward part for a technician.
Tools and parts
- Fine sandpaper
Fireplace thermocoupleSearch: “gas fireplace thermocouple replacement”
When to call a pro
Call a gas fireplace technician if the pilot won't hold after cleaning, or to replace a worn thermocouple.
Safety
Use caution
Always wait the full clearing time before relighting and stop immediately if you smell gas.