Why is my Heater Blowing Cold Air?


The top 7 reasons your heater or furnace is blowing cold air and how to fix it

If you notice that your furnace is blowing cold air instead of warm air, this may be a sign that there is a problem with your gas supply, air filter, condensate lines, or flame detector. These issues can be resolved quite simply on your own by cleaning or replacing one or more of these gas furnace components. In this blog, we will cover each of these issues and the best ways to fix them.

Why your furnace is not blowing warm air:

Broken Pilot Light

If your furnace is producing cold air, it might be time to check the pilot light on your gas heating system to ensure it’s working properly. The pilot light on a gas furnace is intended to ignite the burners so that your heater can produce warm air. If your gas furnace is older, there’s a good chance the pilot light is the root of the cause. If you are able to locate the instruction guide that came with your system, follow the steps for troubleshooting the pilot light on your system for best results.

If you do not have the instructions to your system, you can try to locate the pilot light assembly and reset switch. The reset toggle is typically toward the bottom of the furnace. If you find it, switch it to the OFF position to temporarily turn off the gas. If you are having trouble locating the reset switch, refer to your furnace’s user manual. 

After waiting 3-5 minutes, you can try switching the reset toggle to the ON position to allow the system to dispose of excess gas in the chamber of your furnace. Then you can toggle the reset switch to the PILOT position to allow gas to be transferred to the pilot light. Once you’ve successfully changed the setting on your furnace, you can locate, press, and hold the reset button, while carefully holding a match in front of the pilot light. You should notice the formation of a flame coming from the pilot light. Once you are able to ignite a flame, you will need to release the reset button. If you’ve completed each of these steps successfully, you have successfully re-lit the pilot light, which should activate heat in your home. 

DISCLAIMER: **If you do not feel comfortable attempting this on your own, it is always safest to call in an experienced HVAC professional to assist you. Give FiveStar a call at (615) 382-8131 for same day HVAC service today!** 

Dirty Air Filter is Restricting Airflow

If you notice that your furnace’s air filter is covered in thick dust, soot, or other build-up, there is a good chance that it is blocking proper air flow from your gas furnace. Some of the easiest ways to detect if your air filter is dirty are longer-than-normal heating cycles or overheating issues. When your heating system overheats, it most likely will begin to blow cold air throughout your home. In most cases, simply replacing the dirty air filter with a new one is the best way to resolve this issue and restore the heat in your home. The new air filter will allow the proper amount of air to pass through the furnace, therefore it should no longer overheat. 

Dirt or Build-Up on the Flame Detector

There are several types of gas furnaces that do not utilize a pilot light to activate the production of warm air. Furnaces that do not have pilot lights have a component called a flame detector that manages the successful completion of each heating cycle. Sometimes the flame detector can get covered in dust or debris, and that’s when you will begin to discover cold air blowing from your furnace. The simple fix is to just clean the flame sensor in your furnace. The other option is to call on our team of professional HVAC technicians to make sure the job is done safely and effectively. 

Clogged Condensate Lines

If you’ve noticed your furnace malfunctioning or blowing cold air throughout your home, you may have a blockage in your condensate lines. Most modern furnaces are designed to reduce excess moisture automatically. However, if there is a blockage in the condensate lines, the burners will turn off and cause the heating system to blow out cold air. 

Low Gas Supply

When the gas supply in your home is low, you will likely notice cold air blowing through your heater. This could mean that there is an issue with your home’s gas line. Your furnace is engineered to automatically turn off when it is not receiving enough gas to properly perform its normal heating process. In this case, it is recommended that you reach out to an experienced HVAC technician who will assess your gas furnace and make the necessary repairs. 

Thermostat Setting is Set to ON instead of AUTO

If your heater is blowing cold air instead of warm air, it is important for you to check the setting on your thermostat. If your thermostat is set to the ON setting, this means your furnace will continuously run throughout the day, even when it’s not producing any heat. Make sure you toggle your thermostat to the AUTO setting to ensure that the gas furnace in your home is only running during its normal heating cycle

Damaged Ductwork 

The ductwork in your home may develop holes or cracks over long periods of time. The openings are allowing cold air to seep into the air ducts. So even if your furnace is working properly and is producing warm air, it could begin to leak out by the time it has traveled all the way to your vents. Having a professional HVAC technician come out and inspect and seal your vents so that warm air can travel through much more efficiently.

Professional Furnace Repair & Installation Services

If your home’s furnace is blowing cold air, call FiveStar at (615) 382-8131 or schedule an appointment with us online to receive assistance as soon as possible. Our team is equipped for all kinds of furnace repair and installation services in Nashville and surrounding areas, such as Brentwood, Hendersonville, and Franklin. We also offer other HVAC services like air conditioner repair and replacements. We will make sure to keep your home warm all winter and cool all summer long.