From the hallway, a furnace that will not heat looks the same no matter what broke. Inside the cabinet, though, everything happens in a strict order: inducer on, pressure switch closed, igniter glowing, gas valve open, burners lit, flame proven, and finally the blower sending heat through the house. Most of the diagnosis comes down to finding the broken link. In Lewisville homes, it tends to be the same handful of culprits: a flame sensor coated in oxide, a hot surface igniter cracked by thermal cycling, a pressure switch held open by a tired inducer or a plugged condensate trap, or a control board with a burned relay.
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. These are the signals our technicians see most often:
- A fan that keeps running while the registers blow cool air
- Grinding or high-pitched squeals from the blower
- Loud booms at startup caused by delayed ignition
- Repeated shutdowns just seconds after the burners light
- Water, rust stains, or black soot around the flue or cabinet
- A flame that burns soft and yellow rather than steady blue
- The igniter glows and clicks, yet no flame ever appears
- Short cycling every few minutes without reaching the setpoint
Don't Wait for a Total Failure
A failing capacitor, clogged condensate drain, or dirty flame sensor rarely fixes itself and usually gets more expensive to address the longer it runs. At the first hint of a problem, call (469) 423-7641 for a fast inspection.
