Why Is My Furnace Blowing Cold Air? A Comprehensive Guide

As temperatures drop and winter sets in, your furnace becomes an essential part of keeping your home warm and cozy. However, there's nothing more frustrating than discovering that it is blowing cold air instead of the comforting warmth you expect. If you've found yourself in this situation, you're not alone. In this blog post, we'll explore the common reasons why your furnace might be blowing cold air and what you can do to fix the issue.

Understanding Your Furnace

Before we dive into the reasons behind a furnace blowing cold air, it's important to have a basic understanding of how a furnace works. Furnaces are designed to heat your home by taking in cold air, heating it, and then distributing it through your home's ductwork. They achieve this through various components, including a burner, heat exchanger, blower fan, and thermostat.

Common Causes of a Furnace Blowing Cold Air

Thermostat Settings:

One of the simplest explanations for a furnace blowing cold air is an issue with your thermostat. Check your thermostat settings to ensure it's set to "Heat" mode, and the temperature is set higher than the current room temperature. If the thermostat is set incorrectly, it will not signal the furnace to heat the air properly.

Pilot Light or Ignition Problems:

If your furnace uses a pilot light or electronic ignition system, problems in this area can cause cold air to blow. A malfunctioning ignition system may fail to ignite the burner, preventing the furnace from producing heat. In the case of a pilot light, it may have gone out or needs to be relit.

Dirty or Clogged Filters:

Dirty or clogged air filters can restrict airflow, causing your furnace to overheat and shut down the burners prematurely. When this happens, the furnace may blow cold air as a safety measure. Regularly changing or cleaning your filters is crucial for proper furnace operation.

Gas Supply Issues:

If you have a gas furnace, a lack of gas supply can result in cold air blowing from your vents. Ensure that the gas valve is open and that there are no gas leaks. If you suspect a gas issue, it's essential to contact a professional immediately for safety reasons.

Malfunctioning Blower Fan:

The blower fan in your furnace is responsible for circulating heated air throughout your home. If it's not working correctly, you may experience cold air blowing from the vents. Common issues include a faulty motor, loose belts, or debris blocking the fan.

Heat Exchanger Problems:

A cracked or damaged heat exchanger can lead to cold air being blown into your home. This is a serious issue that can also pose safety hazards, as it may allow harmful gases, such as carbon monoxide, to escape. If you suspect a heat exchanger problem, call a professional immediately.


When your furnace is blowing cold air, it can be uncomfortable and frustrating, especially during the winter months. While some issues can be resolved with simple troubleshooting, others require the expertise of a professional HVAC technician. Regular maintenance and timely repairs are essential for keeping all your HVAC systems in good working condition and ensuring your home stays warm and comfortable throughout the entire year. If you're unsure about the cause of your furnace issue or if it's a complex problem, don't hesitate to seek professional help to diagnose and resolve the issue promptly. Stay warm and cozy!

Here at Kennon Heating & Air Conditioning we want you to enjoy your home to the fullest. That starts with making sure that the air in your home is clean and at the perfect temperature for you. If we can help in any way, please contact us via email or phone (678) 251-9776. Stay cool, stay cozy.