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Furnaces in Kankakee County run about eight months a year, October through May. That is most of the year spent cycling on and off, heating the house through the night and into the next morning. An igniter or a blower motor built for that kind of duty still wears with use. Eight months of runtime means more cycles than a furnace in a milder state ever sees, and more cycles is what ages the parts inside. When something starts acting up here, it's usually that wear catching up with the unit, not a defect or bad luck. Worth having someone look at the actual part before replacing anything.
NOAA nClimDiv, 1991–2020 normals
An igniter fails a little more each time it heats up and cools down, not all at once.
That's why a furnace can light fine for years, then quit on a morning that's no colder than the last one.
If your furnace came with a house built in that era, it may be nearing the end of what it can give you. A furnace that old has either been replaced once already or is running well past when most get swapped out. Before paying for a major repair, ask the technician straight out how much life is left in the unit. A cracked heat exchanger or a failing control board on a furnace that age can cost more to fix than the furnace is worth keeping. That's a different question than how old the house is. It's about what shape this particular furnace is in, and that's worth finding out before any big repair gets approved.
Eight months of runtime a year adds up to a lot of cycles on an igniter or a blower motor. Have the actual part checked before deciding what it needs.
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A furnace rarely quits without warning. It tells you first. Short cycling is one of the clearest signs: the burner fires, runs for a minute or two, then shuts off before the house warms up, and starts again a few minutes later. That usually means a flame sensor that's coated and can't confirm the flame, or a filter so clogged the furnace overheats and trips its limit switch. A burner that won't light at all, after you hear the igniter glow or click, often means the igniter itself is on its way out. Listen for sounds that weren't there before: a squeal from the blower motor, a bang when the burners light, a rattle that comes and goes. Air coming out the vents weaker than it used to, or noticeably cooler, points to the blower or the heat exchanger rather than the thermostat. None of these mean the furnace is done. They mean a part is failing, and most of the time that part can be named and replaced before it takes anything else down with it.
Make sure it's set to heat, not just fan, and the temperature is set above room temperature. Check the batteries if it has a screen that looks dim or blank. A thermostat that lost power or got bumped into the wrong mode looks exactly like a dead furnace, and it costs nothing to rule out.
Pull the filter and hold it up to a light. If you can't see through it, replace it, since a blocked filter can starve the furnace of airflow and shut it down on purpose. Then check that the furnace's power switch, the one that looks like a light switch near the unit, is flipped on. Also check the breaker it runs on. These take a minute to check and they're the ones a homeowner can actually fix without tools.
Estimates for a typical Kankakee County home, compared with an older unit built to the previous federal minimum, from EIA household energy data, Illinois 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.
A repair decision really comes down to two things: what's actually broken, and what else on the furnace is close behind it. A cracked heat exchanger is the clearest line. It can't be patched, and a furnace that fails there needs replacing, not fixing. Most other failures aren't like that. A blower motor, an igniter, a control board, these can be swapped on their own without touching the rest of the system, and doing so brings the furnace back to where it was before the part failed. The harder call is a furnace where one part just failed and others are close to the same age. A technician can tell you whether the rest of the unit is still sound or whether you'd be paying to fix one part on a furnace that's about to need another. That answer comes from looking at the unit, not from how old the paperwork says it is.
