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As the chill of winter settles in, there’s nothing quite as unsettling for homeowners than to wonder why my furnace is not working. Luckily, even though furnace issues can be common, especially for older models, many solutions help warm your home.

Understanding the issues and solutions is key to keeping your home comfortable, whether it’s sudden heat loss, strange noises, or furnace issues. So, if you’ve ever asked, “Why has my furnace stopped working?” you’re in the right place. Let’s equip you with the information to restore warmth to your home!

10 Common Furnace Issues That Could Reduce Efficiency

HVAC systems, such as furnaces, can have intricate components that might feel overwhelming. Let’s simplify things by looking at the 10 most common issues that may impact your home heater from not working and will require professional maintenance or repair.

HVAC Technician replacing the air filter in a furnace

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1. Dirty air filter

Dirty filters reduce the amount of airflow through your home, which causes your home to not heat properly. Solution: Replace air filters regularly. Base the frequency on household needs-Do you have pets or allergies? Are you doing construction?

2. Furnace isn’t heating enough

A common issue is a clogged air filter, which is an easy fix-simply replace the filters. Another possible cause might be your furnace is too small for your home’s needs. Solution: Have a licensed HVAC professional evaluate why your furnace isn’t heating enough.

3. Blower motor not blowing

There are various reasons why your furnace blower isn’t working. A major cause comes when dust accumulates, resulting in weakening strength and having a furnace fan not working. This causes it to turn on and off repeatedly. Solution: Replacing the motor or limit switch or lubricating moving parts.

4. Pilot light or ignitor malfunctioning

The furnace pilot light is used to ignite the natural gas. When its blue flame goes out, your furnace won’t start. Solution: Re-ignite the flame where possible, or replace the ignitor.

Woman on the phone with an HVAC company because the thermostat isn't working

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5. Thermostat malfunctioning

Your thermostat is the signalling tool between you and your furnace. Incorrect settings or malfunctioning sensors are a big reason why your furnace isn’t working. Solution: Check the batteries or replace a faulty thermostat.

6. Furnace constantly turning on and off

If your furnace keeps switching on and off, it could mean your filters are clogged or your thermostat isn’t set properly. Solution: Ensure your thermostat isn’t near a heat source or draft, and clean/replace air filters.

7. Furnace making strange noises

A furnace making odd noises might not affect your heating now, but is a warning sign of future issues. If your furnace starts making noises that resemble something lurking in your basement, it’s usually caused by loose components or worn-out mechanisms within the unit. Solution: Tighten loose parts or replace pieces near the end of their life.

Gas valves for HVAC unit

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8. Clogged up gas valve

Gas valves ensure they provide the correct amount of gas to the burners. Sometimes gas valves may become clogged or even sticky, resulting in your gas furnace not working. Solution: Clean the gas valve or replace it if necessary.

9. Flame sensor is dirty or corroded

This is a critical part of a well-running furnace and is a good spot to check why your furnace isn’t turning on. The sensor ensures there’s always a burning flame. This must function properly as it will completely shut down the heating system to prevent carbon monoxide poisoning or worse, an explosion. Solution: Clean the sensor or replace it.

10. Wear and tear

Over time, normal furnace use causes wear and tear, which can lead to heat regulation problems, airflow issues, or even a complete system breakdown. Solution: Change filters regularly and ensure you have a proper maintenance plan in place.

Sometimes the toughest part can be determining the cause of your furnace not working. There are many ways to troubleshoot the common problems you may have. The homeowner can solve many issues, but we recommend consulting an expert.

Woman standing in front of furnace that’s not working and calling for maintenance

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Remove the Worry of a Furnace Not Working

Most common furnace issues can be detected, and even prevented before you experience a home heater not working. The best way to ensure you don’t run into problems is by having a furnace maintenance plan. For as little as $7.99/month, you can find a plan with LG Home Comfort that suits your needs.

Maintaining a furnace on your own is a complicated task, and should be left to professionals. Trust LG Home Comfort, your reliable HVAC partner, to keep your furnace running properly. Whether it’s a repair, installation, or maintenance, we’re experts in HVAC and take pride in keeping homes comfortable, safe, and warm.

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Raj Bhavra (Senior Vice President - Operations)

Raj Bhavra leads operations at LG Home Comfort, overseeing installation standards and service delivery across Ontario. TSSA-certified, he specialises in cold-climate heat pumps, high-efficiency furnaces, air conditioning systems, and tankless water heaters ensuring every project is built for efficiency and long-term performance for homeowners.

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