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 Downey, CA, 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
Recognizing the warning signs early can save you time and money. These are the signals our technicians see most often:
- A bang or boom when the burners ignite late
- The blower runs constantly but the air never warms
- Short cycling every few minutes without reaching the setpoint
- Rust streaks, soot, or water around the cabinet or flue
- Clicking and a glowing igniter with no burner flame
- Yellow, wavering burner flames where they should be sharp blue
- Grinding or high-pitched squeals from the blower
- Repeated shutdowns just seconds after the burners light
Don't Wait for a Total Failure
Most HVAC failures start small, a weak capacitor, a squealing blower, a system that runs a little longer each week. Call (562) 265-4551 at the first sign of trouble.
