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 Mesquite, 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
The sooner you notice these red flags, the easier and cheaper the fix. Watch for these telltale signs:
- Yellow, wavering burner flames where they should be sharp blue
- The furnace clicks and glows but the burners never light
- Squeals, scrapes, or grinding noises behind the blower door
- 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
- Soot, rust, or moisture near the furnace cabinet or vent pipe
- Loud booms at startup caused by delayed ignition
- A fan that keeps running while the registers blow cool air
Act Before It Gets Worse
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) 920-8561 for a fast inspection.
