Furnace Maintenance Checklist
Most emergency no-heat calls trace back to something on this list — a filter that never got changed, a vent buried under snow, a flame sensor no one cleaned. Here is what you can check yourself, what a technician should handle, and what it actually costs.
The DIY Checklist
These tasks are safe for any homeowner and take a few minutes each. None of them require opening the furnace cabinet or touching the gas line — if a step involves that, it belongs to a licensed technician (see below).
Replace the Air Filter
Every 1–3 monthsA clogged filter restricts airflow, forces the furnace to work harder, and is the single most common cause of no-heat service calls. Hold it up to a light — if you cannot see through it, replace it.
Clear Vents and Registers
SeasonalVacuum dust from supply and return vents, and make sure none are blocked by furniture, rugs, or curtains. Blocked airflow strains the blower motor the same way a dirty filter does.
Test Carbon Monoxide Detectors
MonthlyCO detectors should be installed near the furnace and outside every bedroom. Press the test button monthly and replace batteries twice a year — this is the single most important safety check on this list.
Check Thermostat Settings and Batteries
FallConfirm it is set to HEAT, not COOL, and the fan is on AUTO. If the display is blank or unresponsive, dead batteries are the most common cause — not a furnace fault.
Clear the Space Around the Furnace
OngoingKeep at least 24 inches of clearance around the unit. Do not store boxes, paint, cleaning supplies, or anything flammable near the furnace or its air intake.
Listen for New Noises
OngoingBanging, squealing, or rattling on startup or shutdown usually means a loose part or worn motor bearing. Catching it early is a $150–$500 repair; ignoring it can turn into a $1,000+ one.
Check the Condensate Line
Fall (high-efficiency units only)If your furnace is 90%+ AFUE, it drains condensation through a small plastic tube. Look for standing water near the base of the unit — a clogged line is a common cause of unexpected shutdowns.
Look at the Flame
OngoingThrough the viewing window, the flame should be steady and blue. A yellow, orange, or flickering flame signals incomplete combustion and needs a professional inspection — do not ignore this one.
Keep the Exterior Vent Clear of Snow
WinterHigh-efficiency furnaces vent through a PVC pipe on an exterior wall. After every snowfall, check that it is not buried or blocked — a blocked vent will shut the furnace down as a safety measure.
What a Professional Tune-Up Covers
Gas appliance work is legally regulated in Ontario — burner adjustments, gas pressure testing, and heat exchanger inspections require a TSSA-certified technician. A proper annual tune-up covers:
See our full tune-up checklist and plan pricing- Inspect the heat exchanger for cracks or corrosion
- Test gas pressure and burner flame quality
- Clean the burners and flame sensor
- Measure blower motor amp draw and inspect the belt
- Test all safety controls and limit switches
- Measure carbon monoxide output at the flue
- Inspect flue pipe and venting for leaks
- Calibrate the thermostat
Best Time to Book
September or October, before the first cold snap. HVAC companies book up fast once temperatures drop, and a small issue caught in the fall is a scheduled visit — the same issue ignored becomes a January emergency call.
What It Costs
A one-time furnace tune-up runs $120–$180. If you also have central air, a maintenance plan covering both systems is usually cheaper per visit and adds priority scheduling plus a repair discount.
Stop and Call If You Notice This During Any Check
A gas odour (rotten eggs), a yellow or flickering flame, soot or rust around the cabinet, or a carbon monoxide detector that will not stop alarming are not maintenance items — they are safety issues. Shut the furnace off, leave the area if you smell gas, and call for emergency service immediately.
Furnace Maintenance FAQs
How often should I get my furnace serviced?
Can I do furnace maintenance myself?
What does a professional furnace tune-up include?
How much does a furnace tune-up cost in Toronto?
Does furnace maintenance actually prevent breakdowns?
When is the best time to schedule furnace maintenance in Toronto?
Book Your Fall Tune-Up
TSSA-certified technicians, upfront pricing, and a full inspection before heating season starts. Serving all of Toronto and the GTA.