Every time your thermostat calls for heat, the furnace works through a fixed checklist. The inducer motor starts and proves draft by closing a pressure switch, the hot surface igniter heats up, the gas valve opens, the burners light, and the flame sensor confirms there is fire. Only after all of that does the blower start pushing warm air into the house. Finding the step that fails is most of the job. Around Visalia, CA, the usual failure points are a flame sensor fouled with oxide, an igniter cracked by years of heating and cooling, a pressure switch that stays open because of a weak inducer or a clogged condensate trap on a high-efficiency unit, and control boards with burned relays. Any one of them halts the startup, and from the hallway they all look alike.
When the AC quits in summer, see AC Repair.
Warning Signs for Furnace Repair
Catching these issues early helps you avoid costly problems. Keep an eye out for the following clues:
- Short cycling every few minutes without reaching the setpoint
- A bang or boom when the burners ignite late
- Burners light, run a few seconds, then shut down repeatedly
- Air moving through the vents that never gets warm
- The igniter glows and clicks, yet no flame ever appears
- Squealing or grinding from the blower compartment
- A pilot or burner flame that is lazy yellow instead of crisp blue
- Soot, rust, or moisture near the furnace cabinet or vent pipe
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. Call (559) 337-5468 at the first sign of trouble.
