Gas fireplace pilot light will not stay lit

A gas fireplace pilot that lights but goes out when you let go of the knob usually has a thermocouple or thermopile that is no longer holding the gas valve open, or a pilot flame that is no longer reaching it. In Sioux Falls the typical fix is a $150 to $300 diagnostic service call plus $200 to $400 installed for a thermocouple or thermopile, or $300 to $600 for a whole pilot assembly. A failed gas valve is the less common answer, at $500 to $1,000 installed. We give the firm number once we have seen the unit.

Check this first

These checks are safe for a homeowner and take a few minutes. Stop at any point if you smell gas, and follow the steps on our gas smell page instead.

• Is gas reaching the house? If other gas appliances light, the supply is on. If none do, call the utility first.
• Is the fireplace shutoff open? The City of Sioux Falls homeowner guide calls for a dedicated shutoff at every gas appliance, so there is usually a valve near the fireplace, often behind the lower louver. A handle that lines up with the pipe is open.
• On propane, is there fuel in the tank? Read the gauge. Propane is a bigger share of home heating in the countryside than in town: the Census puts bottled or tank gas at 4.7% of occupied homes in Minnehaha County and 7.0% in Lincoln County, against 1.7% inside Sioux Falls.
• Give it time between tries. Napoleon’s millivolt manual says the valve carries an interlock that will not let the pilot relight until the thermocouple has cooled, and to allow about 60 seconds. Pressing the knob again straight away achieves nothing.
• Look at the pilot through the glass. Note whether it is small, yellow or leaning away from the rod.

Leave the glass in place. Heat & Glo’s manual says glass removal is a job for a qualified service technician, and the gasket seal matters on a direct-vent unit.

Causes, fixes and typical cost

Napoleon’s troubleshooting chart gives the same three reasons for a pilot that goes out when the knob is released: the pilot flame is not engulfing the thermocouple, the thermocouple is shorting or faulty, or the valve is faulty. The manual says the flame must envelop the upper 3/8 to 1/2 inch of the thermocouple and thermopile. Dust, lint or a partly blocked orifice can shrink a pilot below that mark without it looking very different to you.

A thermocouple makes a small voltage when the pilot heats it, and that voltage holds the safety valve open. When it falls short, the valve shuts the instant you let go, which is the safety system working. Our techs take the reading before replacing anything, so a valve is only condemned when the numbers point at it. Napoleon also says its appliance requires a fast-acting thermocouple supplied by the maker, one reason we fit the part listed for your model rather than a universal one. More on how that test runs is on our pilot light and ignition repair page.

Why it shows up in the fall here

NOAA’s 1991 to 2020 normals for Sioux Falls show 162 nights a year at or below freezing and a January normal low of 8.5 F, so a fireplace here can see steady use from October on. Dust and spider webs that built up in the pilot hood over the summer can be the whole problem on that first lighting. Heat & Glo lists an inspection of pilot flame pattern and strength as a yearly technician task, and our annual service covers it before the cold arrives.

When to call us

Call if the pilot still drops after the checks above, if it stays lit only while you hold the knob, or if you have relit it more than once in a day. Repeated attempts can let gas collect in the firebox. Every typical part price is on our pricing page.