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 start pushing warm air into the house. Finding the step that fails is most of the job. Around Oak Park, IL, the usual failure points are an oxide-coated flame sensor, 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
Spotting the early warning signs lets you act before the problem gets expensive. Here are the most common indicators that it's time to call a professional:
- Squeals, scrapes, or grinding noises behind the blower door
- Flames that start, last a few seconds, and go out again and again
- The igniter glows and clicks, yet no flame ever appears
- Soot, rust, or moisture near the furnace cabinet or vent pipe
- A bang or boom when the burners ignite late
- Frequent on-off cycling that never reaches the thermostat setting
- Yellow, wavering burner flames where they should be sharp blue
- The blower runs constantly but the air never warms
Act Before It Gets Worse
What seems like a minor issue today can take out a compressor or heat exchanger tomorrow. If you notice any of these signs, call (708) 536-4740 for a prompt inspection.
