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 Dearborn, MI, 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.
Cooling trouble instead? See AC Repair.
Warning Signs for Furnace Repair
Catching these issues early helps you avoid costly problems. Watch for these telltale signs:
- Squealing or grinding from the blower compartment
- Soot, rust, or moisture near the furnace cabinet or vent pipe
- Booming or banging at light-off from delayed ignition
- A furnace that shuts off every few minutes before the house warms up
- Repeated shutdowns just seconds after the burners light
- The blower runs constantly but the air never warms
- A pilot or burner flame that is lazy yellow instead of crisp blue
- The furnace clicks and glows but the burners never light
Act Before It Gets Worse
A failing capacitor, clogged condensate drain, or dirty flame sensor rarely fixes itself and usually gets more expensive to address the longer it runs. At the first hint of a problem, call (313) 251-3680 for a fast inspection.
