Why fall and spring
A furnace sits idle from about May to October, and an air conditioner from September to June. The parts that fail first, like igniters, flame sensors, capacitors and drain lines, tend to fail on the first day they're asked to work hard. In Ottawa that's the first cold night of the fall and the first humid week of summer, which is exactly when everyone else is calling too.
The spring air conditioner check
- Outdoor coil cleaned and fins straightened
- Capacitor, contactor and wiring tested
- Refrigerant pressures and temperatures checked
- Indoor coil and condensate drain checked and cleared
- Temperature drop across the coil measured
Heat pumps get both checks, because they work in both seasons.
What you can do between visits
- Change the filter. Follow the filter's label. A thin one-inch filter needs changing far more often than a deep media filter.
- Keep the outside clear. Furnace vents free of snow, the outdoor unit free of leaves and clippings.
- Test your carbon monoxide alarms. Ontario requires one next to every sleeping area in a home with a fuel-burning appliance, and since January 1, 2026, on every storey too.