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 South Lyon, MI, 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.
Cooling trouble instead? See AC Repair.
Warning Signs for Furnace Repair
The sooner you notice these red flags, the easier and cheaper the fix. Here are the most common indicators that it's time to call a professional:
- Booming or banging at light-off from delayed ignition
- Clicking and a glowing igniter with no burner flame
- Air moving through the vents that never gets warm
- Repeated shutdowns just seconds after the burners light
- Water, rust stains, or black soot around the flue or cabinet
- Frequent on-off cycling that never reaches the thermostat setting
- Yellow, wavering burner flames where they should be sharp blue
- Squealing or grinding from the blower compartment
Don't Wait for a Total Failure
Most HVAC failures start small, a weak capacitor, a squealing blower, a system that runs a little longer each week. Call (248) 260-5437 at the first sign of trouble.
