Furnace Repair in St. Louis, MO
Furnaces here run from October through April. If yours quits, tell us what it's doing and a licensed contractor who covers St. Louis will get in touch.
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Seven months of heat, on a grid that doesn't always hold
St. Louis asks a furnace to run from October through April, seven months a year. On winter nights that average 26°F from December through February, the burner is cycling on and off for hours at a stretch, and every cycle wears on the igniter and the flame sensor. Most homes in the county heat with gas, so when the igniter finally gives out, the burner won't light at all, and the house goes cold fast.
The area has logged nine winter storms and 28 damaging wind events over the past ten years, and storms like that knock out power. In Missouri, 19% of households went at least 24 hours without power in 2024. A furnace with a dead blower or a dead control board won't run even if the gas is on, and that's the moment most people notice something is wrong.
- 7 months
- October through April, your furnace is on duty
- 26°F
- the average winter night it heats against
- 67%
- of homes here heat with gas, so most furnaces here burn gas
- 9 winter storms
- in ten years, the nights a failure hurts most
NOAA nClimDiv, 1991–2020 normals
A new furnace would cut about $180 a year off heating for a typical St. Louis home.
Estimates for a typical St. Louis home, compared with an older unit built to the previous federal minimum, from EIA household energy data, Missouri fuel prices and NOAA climate normals. Your home will differ.
Repair makes sense when one part has failed and the heat exchanger is sound.
Replacement makes sense when the heat exchanger is cracked or the furnace keeps needing parts.
- Why won't my furnace turn on?
- Check the thermostat first. It needs power, and it needs to be set to heat at a temperature above the room. If the thermostat looks right, check the furnace switch, which looks like a light switch near the unit, and make sure it's on. A tripped breaker or a furnace door that isn't latched shut will also keep it from starting. If none of that explains it, the igniter or a safety switch inside the furnace may have failed, and that calls for a contractor to check.
- Why is my furnace blowing cold air?
- Most often the blower is running before the burners have caught up, which happens for a short time at the start of a cycle and isn't a problem. If cold air keeps coming the whole time it runs, check the thermostat fan setting. Set to "on," the fan runs constantly, including between heating cycles, so it will feel cold in between. Set to "auto," it should only blow once the furnace is actually producing heat. If it's set to auto and still blowing cold, the igniter or gas valve may not be lighting the burners, and that needs a contractor to look at.
- Why won't my furnace pilot light stay lit?
- A pilot light that won't stay lit usually means the thermocouple has worn out. That's the small part that sits in the pilot flame and tells the gas valve the flame is present. When it fails, the valve shuts off the gas as a safety measure, even though the pilot was burning fine a moment before. A draft blowing out the flame is another possibility, worth checking before anything else. If relighting it doesn't hold, the thermocouple needs replacing, and a contractor can do that.