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 Shawnee, KS, 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.
Warning Signs for Furnace Repair
Recognizing the warning signs early can save you time and money. Here are the most common indicators that it's time to call a professional:
- The igniter glows and clicks, yet no flame ever appears
- Rust streaks, soot, or water around the cabinet or flue
- Squealing or grinding from the blower compartment
- Booming or banging at light-off from delayed ignition
- Frequent on-off cycling that never reaches the thermostat setting
- Burners light, run a few seconds, then shut down repeatedly
- A fan that keeps running while the registers blow cool air
- A flame that burns soft and yellow rather than steady blue
Act Before It Gets Worse
Left unchecked, even a small fault or temperature swing often signals a system working its way toward a breakdown. Call (913) 452-5466 at the first sign of trouble.
