Every time your thermostat calls for heat, the furnace runs 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 begin sending warm air into the house. Finding the step that fails is most of the job. Around Lebanon, PA, 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. Each one 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
The sooner you notice these red flags, the easier and cheaper the fix. Keep an eye out for the following clues:
- The blower runs constantly but the air never warms
- Booming or banging at light-off from delayed ignition
- Squealing or grinding from the blower compartment
- Clicking and a glowing igniter with no burner flame
- Burners light, run a few seconds, then shut down repeatedly
- Water, rust stains, or black soot around the flue or cabinet
- A furnace that shuts off every few minutes before the house warms up
- Yellow, wavering burner flames where they should be sharp blue
Act Before It Gets Worse
A failing capacitor, clogged condensate drain, or dirty flame sensor rarely fixes itself and usually gets more expensive to address the longer it runs. If you notice any of these signs, call (717) 200-9284 for a prompt inspection.
