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 Waterloo, IA, 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:
- The blower runs constantly but the air never warms
- Loud booms at startup caused by delayed ignition
- Flames that start, last a few seconds, and go out again and again
- A flame that burns soft and yellow rather than steady blue
- Squealing or grinding from the blower compartment
- Clicking and a glowing igniter with no burner flame
- A furnace that shuts off every few minutes before the house warms up
- Water, rust stains, or black soot around the flue or cabinet
Act Before It Gets Worse
Most HVAC failures start small, a weak capacitor, a squealing blower, a system that runs a little longer each week. Don't wait, call (319) 422-7030 and we'll take a look right away.
