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 St. Joseph, MO, 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.
For air conditioning breakdowns, see AC Repair.
Warning Signs for Furnace Repair
Spotting the early warning signs lets you act before the problem gets expensive. Here are the most common indicators that it's time to call a professional:
- Clicking and a glowing igniter with no burner flame
- A flame that burns soft and yellow rather than steady blue
- Booming or banging at light-off from delayed ignition
- Rust streaks, soot, or water around the cabinet or flue
- Squealing or grinding from the blower compartment
- The blower runs constantly but the air never warms
- A furnace that shuts off every few minutes before the house warms up
- Repeated shutdowns just seconds after the burners light
Don't Wait for a Total Failure
Most HVAC failures start small, a weak capacitor, a squealing blower, a system that runs a little longer each week. At the first hint of a problem, call (816) 208-0722 for a fast inspection.
