How to Check Your Furnace so You’re Ready for Winter

repair technician removing furnace service panel

After your furnace has been switched off during the warmer months, you should run through a checklist so you’re ready for winter. For example, before restarting your furnace, you should assess the air filter, look for holes in the ductwork, and remove dust that has built up in the air vents. 

In this article we’ll detail 8 ways to prepare your furnace for winter.  

8 Ways to Prepare Your Furnace for Winter

Before you start the checklist, do a quick visual inspection of your furnace. Your furnace may be installed in a laundry or equipment room, so remove any items that have stacked up around the furnace. You should also remove any flammable materials you might have forgotten about.

Finally, make sure the combustion air duct is clear of any obstruction. This duct allows the furnace to pull in air and function as needed. 

Now let’s get started…

1. Change the Filter

Senior Man Changing a Dirty Air Filter in a HVAC Furnace
Photo Credit: Backyard Productions / Canva Pro / License

Changing the furnace filter helps ensure your furnace’s longevity. Furnace filters trap particles to keep your unit clean, prevent indoor air contamination, and prevent clogs. If kept unchecked, dirty filters can:

  • Restrict airflow and cause the system to overheat
  • Force the fan motor to overwork (consume more energy)
  • Clog the ductwork system
  • Reduce indoor air quality, possibly aggravating respiratory problems, such as asthma

But how can you be sure that your filter needs replacement or not? Simply remove the filter and hold it up to a light source. If you barely see any light passing through the filter, then you should replace it. 

Pro Tip: To ensure maximum efficiency during the heating season, check the filter monthly and replace as needed. We recommend the use of filters with a high MERV rating. MERV stands for maximum efficiency reporting value, and measures how effective a filter is at removing air particles. The higher the rating, the more efficient the filter is. 

2. Check the Furnace Control Board

Now let’s take a look at your furnace’s control board. Carefully remove the front or access panel to inspect all electrical connections for signs of corrosion. If you own a soft brush suitable for such tasks, gently remove dust from the electronic components. Be careful not to loosen any electrical terminals in the process. 

To be on the safe side and prevent any damage, we recommend hiring an HVAC expert to do this cleaning. 

3. Oil the Furnace Blower

In general, you need to oil the blower motor of your furnace once a year to maintain performance. This component ensures the unit’s effectiveness in distributing hot air to your rooms.

After being switched off for several months, the blower may need to be oiled before restarting. 

You have two options:

  • Spray a lubricant directly into the oil ports. You can purchase lubricant sprays in any local hardware store. 
  • Inject lubricant into the ports with a grease gun (2 or 3 drops)

If strange noises keep coming from the blower even after oiling the ports, call an HVAC pro. 

4. Check for Furnace Leaks

Air and gas leaks in your furnace are a big problem, so here is how to check for them. 

Inspect your ductwork system for holes or gaps that can result in wasted heat. Sealing air leaks is key to maximize your furnace’s performance and ensure proper airflow.

Here are some signs of an air leak:

  • High energy bills: If there’s an air leak, your furnace will have to work much harder. This extra work puts a strain on your unit, which consumes more energy to keep running.  
  • Higher dust levels: Leaking duct systems can pull in dust that’s built up around them, distributing it throughout your home. 
  • Uneven heat distribution: If you notice that some parts of your home are colder than others, then heat isn’t being distributed evenly. This is another clear sign of gaps or holes in the ducts

If you own a natural gas furnace, you should regularly check for gas leaks. Use your ears and nose.

  • Ears: Inspect the gas lines and listen closely for any hissing sound, indicating a gas leak.
  • Nose: If you smell rotten eggs, that’s mercaptan letting you know there’s a gas leak. Mercaptan is an organic gas that’s composed of carbon, hydrogen, and sulfur.  

In you suspect a furnace leak, switch off the unit immediately and call a local HVAC professional. To stop the leaks, the pro will most likely use a liquid sealant or heavy-duty aluminum foil. 

5. Clean the Air Ducts and Vents

Cleaning air ducts
Photo Credit: Bill Oxford / Canva Pro / License

Air ducts are important for any heating system. Furnaces use them to circulate heated air throughout your home. Clean and properly maintained air ducts ensure hot air gets circulated effectively, and they help maintain good indoor air quality. 

In contrast, ducts with high levels of dust restrict air flow and make it difficult for your furnace to distribute heat. This extra struggle can raise your utility bills.

What you need to do:

Clean registers and return vents before the heating season begins. You can use a wet cloth – not soaking wet – to remove dust off the vents and ducts. You should also remove furniture or drapes that block the openings and restrict airflow. 

6. Test Carbon Monoxide Detectors

Carbon monoxide (CO) produced by furnaces in enclosed spaces can be very dangerous and poisonous. CO detectors will make loud beeping sounds when levels start reaching dangerous levels. 

If your CO detectors are operated by batteries, check if they need to be replaced. After inserting new batteries, test the detectors to make sure the beeping alarm sound is loud enough for you to hear. 

If your CO detectors are frequently damaged or not functioning properly, replace them before restarting the furnace ahead of winter. 

If you’re buying new CO detectors, the Environmental Protection Agency recommends devices that are certified to the current Underwriters Laboratory (UL) standard 2034. Just check for a UL certification mark on the packaging, which shows that the CO detector has been tested to nationwide sustainability and safety standards. 

7. Switch the Thermostat to “On”

Photo Credit: RossHelen / Canva Pro / License

Before you switch on your thermostat, check the wire connections under the cover to ensure every wire is properly attached. If you haven’t done so already, replace the batteries with fresh ones. 

If everything checks out, you can take the following steps:

  • Switch the thermostat setting to heat mode (switch it on).
  • Set the temperature a few degrees above the current room temperature.

Note: You should hear your furnace start in a minute or two.

There may be a temporary odor as the furnace burns away dirt and dust buildup inside. This is normal as dust settles on the heat exchanger when it’s not activated. 

If the unit doesn’t switch on, makes strange noises, or keeps releasing a burning odor, switch off the furnace immediately and schedule professional maintenance.

Overall, switching on the thermostat and going through this checklist gives you a better chance of addressing a problem before it gets worse. 

8. Schedule a Professional Inspection

Cleaning certain parts of a furnace is not DIY-friendly and should be handled only by a trained, HVAC professional. Home Gnome connects you to local HVAC pros who will check and maintain your furnace so you’re all set for winter.

The first thing the expert will do is replace your thermostat if needed. You can’t regulate temperatures and switch on the furnace with a damaged one. The expert will then proceed by cleaning the core components of your furnace: 

  • Heat exchanger: This part of a furnace tends to be impacted by frequent dust buildup, and should be brushed and vacuumed. Why can’t you do this yourself? Inspecting, removing, and cleaning the heat exchanger requires special tools and training. 
  • Blower assembly: Ideally, it should be cleaned about twice a year. The openings of the blower tend to become blocked with dust or dirt. Letting pros clean this component will help minimize respiratory problems (asthma, allergies, etc..)
  • Burners: They may be connected through slots or wings. The pro will need to take them apart before cleaning them. Doing this yourself can damage the components and keep the furnace from working properly. 

Main Photo Credit: BanksPhotos / Canva Pro / License

Jeffery Keusseyan

Jeffery Keusseyan is a writer with a knack for research and handiperson skills. He enjoys writing about home improvement projects and efficient ways to maintain your home exterior.