Fall Furnace Tune-Up Checklist for Ontario Homes

What you’ll need

• Correctly sized pleated furnace filter (check the size printed on the old one)
• Vacuum with a brush attachment
• Flashlight
• Screwdriver
• Fresh batteries for the thermostat and CO alarm

Start With a Clean Filter

A clogged filter is the single most common cause of poor heat output and short cycling. Airflow drops, the heat exchanger overheats and the furnace shuts itself down on a safety limit long before the house is warm.

Slide the old filter out and note the arrow printed on the frame — it always points toward the furnace, in the direction of airflow. In a GTA home with pets or ongoing renovation dust, plan on replacing a one-inch filter every two to three months through the heating season.

Test the System Before You Need It

Run a heat cycle on a mild September day rather than discovering a problem at minus fifteen. Set the thermostat about five degrees above room temperature and listen.

You should hear the inducer motor, then ignition, then the blower a few seconds later. Warm air should reach the registers within a minute or two and the furnace should run a full cycle rather than firing and shutting off repeatedly.

• A burning-dust smell for the first few minutes is normal and should fade.
• Repeated clicking with no ignition usually means an igniter or flame sensor issue.
• Short cycling points to airflow restriction, an oversized furnace or a failing limit switch.
• Rattling sheet metal is often just a loose panel screw.

Clear the Vents, Returns and Exhaust

Walk the house and open every supply register, including in unused bedrooms. Closing vents does not save money on a residential forced-air system; it raises static pressure and makes the furnace work harder.

Outside, find the plastic intake and exhaust pipes on the side of the house. Ontario snow drifts and fallen leaves block these every winter, and a blocked exhaust will shut a high-efficiency furnace down or, worse, spill combustion gases.

• Keep 45 cm clear around the outdoor intake and exhaust terminations.
• Vacuum cold-air returns and remove furniture blocking them.
• Check that the condensate drain line runs freely into the floor drain.
• Clear stored boxes at least a metre away from the furnace cabinet.

Carbon Monoxide Alarms Are the Law in Ontario

Ontario's Fire Code requires a working carbon monoxide alarm adjacent to every sleeping area in homes with a fuel-burning appliance or an attached garage. Test yours with the button, replace the batteries and check the manufacture date — CO sensors expire, usually after seven to ten years.

If an alarm sounds, get everyone outside and call 911 or your gas utility's emergency line. Do not go back inside to investigate.

Frequently asked questions

When should I book a furnace tune-up in the GTA?

Late August through October. HVAC companies across Toronto and the GTA fill up as soon as the first cold snap arrives, and emergency rates in December are far higher than a scheduled fall visit.

How often should I change my furnace filter?

Every two to three months for a standard one-inch filter, or monthly with pets, allergies or renovation dust. Thicker four- or five-inch media filters typically last six to twelve months.

Why does my furnace smell like dust when it first runs?

Dust that settled on the heat exchanger over summer burns off during the first cycles. It should clear within 20 minutes; a persistent burning or electrical smell means shut it down and call a technician.