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 Waukesha, 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.
Cooling trouble instead? See AC Repair.
Warning Signs for Furnace Repair
The sooner you notice these red flags, the easier and cheaper the fix. These are the signals our technicians see most often:
- Loud booms at startup caused by delayed ignition
- Short cycling every few minutes without reaching the setpoint
- The igniter glows and clicks, yet no flame ever appears
- Repeated shutdowns just seconds after the burners light
- Yellow, wavering burner flames where they should be sharp blue
- Water, rust stains, or black soot around the flue or cabinet
- Squeals, scrapes, or grinding noises behind the blower door
- Air moving through the vents that never gets warm
Early Action Saves Money
What seems like a minor issue today can take out a compressor or heat exchanger tomorrow. Call (262) 401-5105 at the first sign of trouble.
