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 Garland, 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.
When the AC quits in summer, see AC Repair.
Warning Signs for Furnace Repair
Spotting the early warning signs lets you act before the problem gets expensive. Keep an eye out for the following clues:
- Water, rust stains, or black soot around the flue or cabinet
- Repeated shutdowns just seconds after the burners light
- Clicking and a glowing igniter with no burner flame
- Air moving through the vents that never gets warm
- A furnace that shuts off every few minutes before the house warms up
- Yellow, wavering burner flames where they should be sharp blue
- A bang or boom when the burners ignite late
- Grinding or high-pitched squeals from the blower
Early Action Saves Money
Most HVAC failures start small, a weak capacitor, a squealing blower, a system that runs a little longer each week. At the first hint of a problem, call (972) 920-8553 for a fast inspection.
