A modern furnace runs a strict startup sequence, and knowing where the sequence breaks is most of the diagnosis. The thermostat calls, the inducer motor spins up to prove draft through a pressure switch, the hot surface igniter glows, the gas valve opens, the burners light, the flame sensor confirms fire, and only then does the blower deliver heat to the house. In Madison, WI, the failures cluster at predictable points: a flame sensor coated in oxide that can no longer prove the flame, a hot surface igniter cracked from years of thermal cycling, a pressure switch that will not close because the inducer is weak or the condensate trap on a high-efficiency model has clogged, or a control board with a burned relay. Each one stops the sequence cold, and each one mimics the others from the hallway.
When the AC quits in summer, see AC Repair.
When to Call for Furnace Repair in Madison
Spotting the early warning signs lets you act before the problem gets expensive. These are the signals our technicians see most often:
- A flame that burns soft and yellow rather than steady blue
- A furnace that shuts off every few minutes before the house warms up
- Squeals, scrapes, or grinding noises behind the blower door
- Air moving through the vents that never gets warm
- Booming or banging at light-off from delayed ignition
- Burners light, run a few seconds, then shut down repeatedly
- Clicking and a glowing igniter with no burner flame
- Water, rust stains, or black soot around the flue or cabinet
Early Action Saves Money
A failing capacitor, clogged condensate drain, or dirty flame sensor rarely fixes itself and usually gets more expensive to address the longer it runs. If you notice any of these signs, call (920) 516-9221 for a prompt inspection.
