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9 Things You Can Do To Check Your Furnace Before Winter

Written by Craig Aspinall | Sep 17, 2025 3:28:58 PM

Winter comes fast, and when temperatures drop, you rely on your furnace to keep your home warm and cozy. The last thing you need is a furnace breakdown on the coldest day of the year. Fortunately, you can avoid most heating emergencies by preparing your system for the season ahead.

Whether you're handy around the house or prefer simple maintenance tasks, these furnace checks are manageable for most homeowners. Let's walk through nine things you can do to check your furnace before winter.

Change the Air Filter

Your furnace's air filter works hard to keep dust, dirt, and debris out of your heating system. Over time, this filter gets clogged and restricts airflow, making your furnace work harder to heat your home. A dirty filter forces your system to use more energy and can even cause it to overheat.

Before winter begins, replace the air filter in your furnace. Throughout the winter season, check and replace your filter every one to three months for the best results.

Clean filters improve your indoor air quality and help your furnace run more efficiently. This simple maintenance task can extend your equipment's lifespan and reduce your heating costs throughout winter.

Inspect the Thermostat

Your thermostat controls when your furnace turns on and off, so you want to make sure it works correctly before cold weather hits. First, make sure to switch your thermostat from cooling to heating mode. Set the temperature a few degrees higher than the current room temperature to test if the furnace kicks on.

If your thermostat uses batteries, consider replacing them even if they seem fine. Dead batteries can cause your furnace to stop working. Write the replacement date on the battery compartment so that you remember when they were last changed.

If you have a programmable thermostat, take a few minutes to set your winter schedule. You can set lower temperatures when you're sleeping or away from home and warmer settings when you're active and awake.

Examine Air Vents and Ducts

Your home's ductwork carries heated air from your furnace to every room. Walk through your home and inspect each vent for dust, pet hair, or other obstructions. Make sure to move any furniture items that may block the vents.

If you notice significant dust buildup in your ducts, consider having them professionally cleaned. Clean ducts improve airflow and indoor air quality while helping your furnace operate more efficiently.

Turn on the Heating System

Before you really need heat, test your furnace to make sure it starts up properly. Set your thermostat and listen for the system to cycle on. A properly functioning furnace should start up within seconds.

Watch the furnace through a complete heating cycle. It should run for several minutes, then shut off when the temperature reaches the thermostat setting. If the furnace runs continuously or cycles on and off too frequently, you might have a problem that needs professional attention.

Check that warm air comes out of your vents within a reasonable time after the furnace starts. Cold air blowing from vents could indicate issues with the heat exchanger or other components.

Listen for Unusual Noises

Your furnace makes normal operating sounds, but unusual noises can signal problems. Turn off other appliances and background noise so that you can really listen to your heating system. Banging sounds might indicate loose parts or problems with the heat exchanger.

Rattling noises often come from loose screws, panels, or ductwork. Many of these issues are easy to fix by tightening connections or securing loose components. Whistling sounds usually mean air is escaping somewhere it shouldn't, possibly through damaged ducts or loose connections.

If you hear grinding or squealing noises, your furnace might have worn bearings or belt problems. These issues require professional repair, so don't ignore persistent unusual sounds.

Check for Strange Smells

When you first turn on your furnace after months of inactivity, you might smell burning dust. This odor is completely normal and should disappear within a few minutes as the dust burns off the heat exchanger.

However, other smells can indicate serious problems:

  • Burning plastic or metallic smell: This suggests electrical issues that could create a fire hazard. Turn off your furnace immediately and call a qualified technician to investigate. Don't try to operate the system until a professional determines it's safe.
  • Rotten eggs: This particular odor indicates a possible gas leak. This is a serious safety concern that requires immediate action. Turn off your furnace, leave your home, and call your gas utility company from a safe location. You’ll also want to contact an HVAC service company but be sure to prioritize getting the gas leak addressed.
  • Musty odors: This smell could be caused by a dirty air filter or mold growth in your ductwork. Try changing the filter first, and if the smell persists, contact an HVAC technician for further diagnosis.

Look at the Pilot Light

If you have a gas furnace, it includes a pilot light that ignites the main burner. When your furnace runs, this pilot light should burn with a steady blue flame. A healthy blue flame indicates proper combustion and safe operation.

Yellow or orange flames suggest incomplete combustion, which can create carbon monoxide and other safety hazards. Flickering flames might indicate air drafts or problems with the gas supply. Both situations require professional attention.

Check or Install a Carbon Monoxide Detector

Carbon monoxide is an invisible, odorless gas that can be deadly. Gas furnaces can potentially produce carbon monoxide if they malfunction or aren't properly vented. Every home with a gas furnace should have working carbon monoxide detectors, especially near bedrooms.

Test your existing detectors by pressing the test button. If the alarm doesn't sound, replace the batteries. Even hardwired detectors often have battery backups that need regular replacement.

Schedule a Professional Tune-Up

While you can handle basic furnace maintenance yourself, annual professional service helps catch problems early and keeps your system running efficiently. HVAC technicians have specialized tools and training to inspect components you can't safely check yourself.

During a professional tune-up, technicians clean internal components, check gas connections, test safety controls, and calibrate your system for optimal performance. They can spot worn parts before they fail and cause expensive emergency repairs.

Keep Your Home Comfortable This Winter

There are plenty of things you can do to check your furnace before winter to prepare for the cold months ahead. Regular maintenance prevents most heating emergencies and helps your furnace run efficiently throughout the season.

If your furnace inspection reveals that your heating system needs replacement or major repairs, Capitol Supply and Service specializes in mobile home replacement furnaces and professional service. Our experienced team can help you choose the right heating solution for your manufactured home and ensure it's installed correctly for years of reliable comfort. Contact us today to discuss your heating needs and schedule service for your furnace.