Getting your heating ready before the first cold rain

The ten-minute test run

Pick a mild day, set the thermostat to heat, and raise the setpoint a few degrees above room temperature. You're listening and smelling: the system should start smoothly, warm air should arrive at the registers within a few minutes, and any burning-dust smell should fade within the first fifteen minutes or so (that's summer dust cooking off the heat exchanger — normal once, not every day). Grinding, screeching, repeated start-stop cycling, or no heat at all means you've found the problem in September instead of November, which is exactly the point. Note what you observed — it makes the service call faster and cheaper to diagnose.

Filter and registers

Install a fresh filter (or check your media filter's condition) before the blower starts running daily. If the past summer included a smoke event, don't trust the calendar — a smoke-loaded filter can look passable and still be choking airflow. While you're at it, walk the house and make sure supply registers and return grilles aren't blocked by furniture, rugs, or the summer's rearranging. A heating system starved for return air runs hotter, cycles on its safety limits, and wears out faster — and the fix costs nothing.

The outdoor unit, before the rains

If you have a heat pump, autumn is when Douglas fir needles, maple leaves, and cottonwood debris collect on top of the outdoor unit and against its coil. Once the October rains arrive, that debris mats into a wet blanket that blocks airflow and holds moisture against the fins all winter. Clear the top, gently rinse the coil with a garden hose (never a pressure washer), trim vegetation back to give the unit 18–24 inches of breathing room, and check that the unit still sits level so defrost water drains instead of pooling and freezing on the pad.

Safety checks and the pro tune-up

Press the test button on every carbon monoxide alarm and replace batteries — if you heat with gas, this is non-negotiable, and alarms have expiration dates printed on the back worth checking too. Then schedule the professional tune-up. A fall visit covers the things you can't do yourself: heat exchanger inspection, gas pressure, ignition and flame sensor, safety limit tests, and for heat pumps, defrost operation and backup heat staging. Booking in September or early October beats the first-cold-snap rush, when everyone whose furnace didn't start is calling at once.

Common questions