The Complete Furnace Maintenance Checklist for London, Ontario Homeowners

London winters arrive fast and stay long. A furnace that has not been serviced since last season is a furnace that is more likely to fail on the coldest night of the year. The good news is that most furnace problems are entirely preventable with a consistent annual maintenance routine. This checklist covers everything a homeowner can do themselves and everything that requires a licensed gas fitter.

What You Can Do Yourself

• Replace the air filter every 1 to 3 months depending on filter type and household dust levels. A clogged filter is the single most common cause of furnace breakdowns.
• Clear a 1-metre radius around the furnace of stored items, boxes, and flammable materials.
• Check that all supply and return vents throughout the home are open and unobstructed by furniture or rugs.
• Test your carbon monoxide detector and smoke alarm. Replace batteries if needed.
• Inspect the exhaust flue pipe for visible damage, rust, or disconnected joints.
• Vacuum dust from the blower compartment and burner area if accessible without disassembly.
• Set your thermostat to heat mode and confirm the furnace fires up and runs a full cycle without short-cycling.

What Requires a TSSA-Licensed Gas Fitter

Ontario law requires that any work involving the gas train, heat exchanger, or combustion system be performed by a licensed gas fitter. Attempting these tasks without a licence is both illegal and dangerous. During a professional tune-up, a Corner Gas HVAC technician will:

• Inspect and clean the burners for proper flame pattern and colour. A yellow or orange flame indicates incomplete combustion.
• Test the heat exchanger for cracks using a combustion analyzer. A cracked heat exchanger can leak carbon monoxide into your living space.
• Clean and test the flame sensor, which is responsible for confirming the burner has lit. A dirty flame sensor is one of the most common causes of furnace lockouts.
• Test the ignitor and measure its resistance to predict failure before it leaves you without heat.
• Lubricate the blower motor bearings and check the belt tension if applicable.
• Measure the supply and return air temperature differential to confirm the system is delivering the correct heat rise.
• Test the gas pressure at the manifold to ensure it meets manufacturer specifications.
• Inspect the condensate drain on high-efficiency furnaces and clear any blockages.
• Verify all safety controls including the high-limit switch and pressure switches are functioning correctly.

How Often Should a Furnace Be Serviced in London, Ontario?

Annual servicing is the standard recommendation for all gas furnaces, and most manufacturer warranties require documented annual maintenance to remain valid. The ideal time for a London homeowner is September or early October, before the first cold snap. Booking early also means you avoid the rush that hits every HVAC company in November when the temperature drops overnight and the phones start ringing.

The Cost of Skipping Maintenance

A professional furnace tune-up in London, Ontario typically costs between $120 and $200. The average emergency furnace repair call costs $350 to $700 and often happens on a weekend or holiday when rates are higher. Beyond repair costs, a dirty or poorly calibrated furnace can increase your gas bill by 10 to 25 percent over a heating season. The math strongly favours preventive maintenance.