Pre-winter furnace tune-up: what to do in September and October

Furnaces fail in December for reasons that were visible in October. Condensing furnaces sit idle for months; condensate evaporates from the trap and leaves debris behind, flame sensors collect a season's worth of residue, and filters that served summer cooling stay loaded into the heating season. The classic winter no-heat calls — pressure-switch codes from blocked drains, ignition faults from fouled sensors — are autumn maintenance items.

Booking in September or October also means shorter waits: when the first cold snap hits, every contractor in the region is busy with no-heat calls, and a preventive visit is harder to schedule. The annual maintenance page on this site lists the full scope the visit should cover.

Change or clean the filter and note its size for the next change. Confirm supply registers and return grilles are open and unblocked by furniture. Look at the vent and intake terminations from outside: no nests, leaves, sagging pipe or signs of ice damage from last winter. Confirm the furnace switch and breaker are on and the blower door is seated, and replace thermostat batteries if it uses them.

Walk the condensate path: the drain line to the floor drain or pump should be clear, the pump reservoir empty, and the pump's safety float free. If the furnace has an exterior drain termination, check it is clear before the weather turns.

The maintenance visit is the deep version of the owner checks: combustion analysis, gas-pressure verification, condensate trap and collector-box cleaning, flame-sensor cleaning with flame-signal measurement, ignitor inspection, inducer and blower operation, temperature rise against the rating plate, venting inspection, and a read of the control's stored fault history.

The fault-history read is the part homeowners cannot do: a furnace that quietly logged pressure-switch events or flame losses over the summer is telling the technician something before it becomes a December lockout.

In the first weeks of heating, watch for the things maintenance is meant to prevent: cold air from the registers (burner not lighting), water around the furnace (condensate path), or codes on the display. Manufacturers' installation instructions used across this site call for an annual inspection by a qualified service person; the service record from the visit is also the evidence a warranty claim may ask for.

If you smell gas, or a carbon-monoxide alarm sounds, do not wait for a maintenance appointment: leave the building and call FortisBC at 1-800-663-9911 or 911, then call BC Wide. Maintenance prevents breakdowns; it is not a response to a live hazard.