How a standing pilot system works
A small continuous flame sits next to the burners. A thermocouple or thermopile in that flame generates a tiny voltage from heat. That voltage holds a safety valve open. If the pilot goes out, the voltage disappears, the valve closes, and gas stops flowing — a purely mechanical safety design that works without electricity.
Why pilots go out
| Cause | Sign |
|---|---|
| Failing thermocouple | Pilot lights but goes out as soon as you release the control knob |
| Dirty or partially blocked pilot orifice | Weak, small, or yellow-tipped pilot flame |
| Draft in the furnace area | Pilot blows out during windy weather or when a door opens |
| Blocked or backdrafting flue | Pilot repeatedly extinguishes; possible combustion odors |
| Gas supply interruption | Other gas appliances also affected |
| Failed gas valve | Pilot holds but the main burners never light |
About relighting a pilot
Read the label on your furnace
Many furnaces carry manufacturer relighting instructions inside the access panel. If you are at all unsure, do not attempt it — call instead. Never attempt to relight if you smell gas: leave the house and call the gas utility or 911 from outside. Never hold the gas control knob down repeatedly to force ignition, and never modify or bypass any safety component.
If a pilot goes out once after a windy night, it may simply have been drafted out. If it goes out repeatedly, something has changed and it needs diagnosis — most often a thermocouple losing output, or a venting problem that deserves attention for safety reasons regardless.
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The age question
A furnace with a standing pilot is likely 25 years old or more. That does not mean it must be replaced today — plenty run reliably. It does mean that when something significant fails, the repair-versus-replacement math looks different than on a ten-year-old unit. A standing pilot also burns gas continuously year-round, and these units are typically in the 60–80% efficiency range, so a meaningful share of your gas bill goes up the flue during a long Western New York heating season.
We are not going to tell you an operating, safe furnace must be replaced. We will give you the condition assessment, the efficiency reality, and the repair cost, and let you decide.