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 Detroit, MI, 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
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:
- Squealing or grinding from the blower compartment
- The furnace clicks and glows but the burners never light
- The blower runs constantly but the air never warms
- Burners light, run a few seconds, then shut down repeatedly
- Soot, rust, or moisture near the furnace cabinet or vent pipe
- Loud booms at startup caused by delayed ignition
- A furnace that shuts off every few minutes before the house warms up
- A pilot or burner flame that is lazy yellow instead of crisp blue
Early Action Saves Money
What seems like a minor issue today can take out a compressor or heat exchanger tomorrow. At the first hint of a problem, call (313) 217-8997 for a fast inspection.
