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 San Antonio, TX, 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.
When to Call for Furnace Repair in San Antonio
Catching these issues early helps you avoid costly problems. Keep an eye out for the following clues:
- A bang or boom when the burners ignite late
- The blower runs constantly but the air never warms
- A pilot or burner flame that is lazy yellow instead of crisp blue
- Soot, rust, or moisture near the furnace cabinet or vent pipe
- Clicking and a glowing igniter with no burner flame
- A furnace that shuts off every few minutes before the house warms up
- Flames that start, last a few seconds, and go out again and again
- Squealing or grinding from the blower compartment
Don't Wait for a Total Failure
Left unchecked, even a small fault or temperature swing often signals a system working its way toward a breakdown. If you notice any of these signs, call (826) 212-7453 for a prompt inspection.
