Is Your Furnace Ready for the First Cold Snap?

September is a good time to think about your furnace again. After sitting mostly unused through the summer, your heating system may soon be working every day as temperatures drop across the GTA.

The last thing you want is to discover a furnace problem on the first cold night of the season.

A few simple checks now can help you catch problems before you actually need your furnace.

Here is a simple September furnace maintenance checklist for homeowners, including what you can safely check yourself and when it is better to have a professional inspect the system.

1. Turn Your Furnace On Before You Need It

Do not wait for the first freezing night to find out whether your furnace works.

On a mild September or early October day, switch your thermostat to heating mode and set the temperature a few degrees higher than the current room temperature.

Let the furnace run for a few minutes and check that warm air is coming from the registers.

Pay attention to anything unusual, such as:

• The furnace does not start
• Weak airflow from the vents
• The furnace starts and stops repeatedly
• Unusual banging, rattling, squealing, or grinding sounds
• The air coming from the registers does not seem warm

If something does not seem right, deal with it now rather than waiting for the first cold snap.

2. Check Your Furnace Filter

A dirty filter is one of the simplest furnace problems homeowners can prevent.

A clogged filter restricts airflow and can make your furnace work harder. Carrier recommends homeowners check and replace or clean filters regularly, with the exact interval depending on the equipment and filter. :contentReference[oaicite:2]{index=2}

If your filter looks dirty, replace it with the correct size and type recommended for your system.

Also remember that a filter should not simply be changed once a year. Check it regularly during the heating season, particularly if you have pets, allergies, renovations, or higher household occupancy.

3. Make Sure Your Vents and Returns Are Clear

Look around your home and make sure furniture, curtains, rugs, or other items are not blocking supply registers or return-air grilles.

It is easy to move furniture during the summer and forget that it is covering a vent once heating season begins.

Keeping registers and returns clear helps maintain proper airflow throughout the home.

If one room has always been colder than the rest of the house, however, simply opening a vent may not solve the problem. Airflow, ductwork, insulation, equipment sizing, and other factors may need to be checked.

4. Keep the Area Around Your Furnace Clear

Your furnace needs appropriate clearance and access for safe operation and servicing.

Before heating season starts, look around the furnace and remove boxes, storage items, cleaning supplies, or other clutter that may have accumulated over the summer.

Do not use the furnace room as a general storage area, and never place combustible materials where they could interfere with the equipment or its required clearances.

5. Check Your Thermostat

Your thermostat controls when the furnace operates, so it is worth checking before heating season.

Make sure:

• The thermostat is set to heating mode
• The temperature setting is correct
• The thermostat is responding when you adjust the temperature
• Batteries are replaced if your thermostat uses them
• No unusual schedules or settings are preventing the furnace from running when needed

If your thermostat appears to be working but the furnace does not respond properly, the issue may require professional diagnosis.

6. Check Your Carbon Monoxide Alarms

If your home has a gas furnace or another fuel-burning appliance, carbon monoxide safety should be part of your fall routine.

Check that your carbon monoxide alarms are working and follow the manufacturer’s instructions for testing, batteries, and replacement.

Ontario’s carbon monoxide safety requirements were updated in 2026, so homeowners should make sure their alarms meet the current requirements for their home. :contentReference[oaicite:3]{index=3}

If a carbon monoxide alarm sounds, leave the home immediately and call 911 or your local emergency service from outside. Do not ignore an alarm or assume it is a furnace problem you can troubleshoot yourself.

7. Look at the Furnace Before the Heating Season Starts

You do not need to open the furnace cabinet or attempt to work on gas or electrical components yourself.

Instead, look at the area around the furnace for anything obviously unusual.

For example, take note of:

• Water around the furnace
• Unusual rust or corrosion
• Damaged or disconnected visible components
• Unusual sounds when the furnace runs
• Persistent unusual smells
• Signs that the furnace has been struggling to operate

Do not remove panels or attempt to repair the furnace yourself. Gas, combustion, electrical, and internal furnace components should be handled by a qualified HVAC professional.

8. Schedule Furnace Maintenance Before the First Cold Snap

Homeowner checks are useful, but they are not a substitute for professional furnace maintenance.

An annual professional inspection gives a qualified technician an opportunity to check components that homeowners should not inspect or adjust themselves.

Depending on the furnace and its condition, professional maintenance can include checking areas such as:

• Burners and ignition
• Electrical components
• Blower operation
• Airflow
• Venting
• Safety controls
• Heat exchanger condition
• Combustion and system operation

The exact maintenance procedure depends on the furnace model and manufacturer requirements.

September is a smart time to schedule this service because you can address potential problems before the furnace is needed every day.

Signs Your Furnace Should Be Checked Before Winter

Even if your furnace worked normally last winter, it is worth paying attention to changes when you turn it on this fall.

Consider booking a professional inspection if you notice:

• New or unusual noises
• Frequent cycling
• Weak airflow
• Uneven heating
• The furnace struggles to reach the thermostat setting
• Unexpected increases in energy use
• Repeated repairs
• A furnace that does not start reliably

Finding these problems in September is much better than discovering them when your home is cold.

What If Your Furnace Is Getting Old?

September is also a good time to think about furnace replacement if your current system has become unreliable or repair costs are starting to add up.

You do not have to wait for a complete breakdown to explore your options.

Planning ahead gives you time to compare equipment, installation options, efficiency ratings, warranties, and available rebates or promotions.

If your furnace has already given you warning signs, September is a much better time to make a replacement decision than the middle of a winter breakdown.

Your September Furnace Checklist

Before the first cold snap, make sure you have:

The goal is simple: find problems while you still have time to fix them.

Get Your Furnace Ready for Winter

A furnace that has been sitting through the summer deserves a quick check before it is asked to heat your home day after day.

Furnace & AC Expert provides professional furnace maintenance, repair, and replacement throughout Mississauga, Brampton, Oakville, Etobicoke, Milton, and nearby GTA communities.

If your furnace needs maintenance, is making unusual noises, is not heating properly, or you are considering a new system, our team can help.

Call Furnace & AC Expert at 905-595-0505 to schedule furnace service before the first cold snap.

You can also contact us online to request furnace maintenance, repair, or replacement information.

Carrier Factory Authorized Dealer serving homeowners across the GTA.