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 Eau Claire, WI, the failures cluster at predictable points: an oxide-coated flame sensor, 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
Catching these issues early helps you avoid costly problems. Watch for these telltale signs:
- A furnace that shuts off every few minutes before the house warms up
- The blower runs constantly but the air never warms
- Burners light, run a few seconds, then shut down repeatedly
- Grinding or high-pitched squeals from the blower
- Water, rust stains, or black soot around the flue or cabinet
- Loud booms at startup caused by delayed ignition
- A pilot or burner flame that is lazy yellow instead of crisp blue
- The igniter glows and clicks, yet no flame ever appears
Early Action Saves Money
Most HVAC failures start small, a weak capacitor, a squealing blower, a system that runs a little longer each week. If you notice any of these signs, call (534) 231-2225 for a prompt inspection.
