Why Is My Furnace Blowing Cold Air?

November 17, 2019


If your furnace seems to run well but it blows cold air, there’s a cause for concern. Though furnaces blow cold air for several reasons, there are a few steps you can take before calling Scott-Lee Heating Company in St. Louis. Here are some of the most common reasons for a furnace to put out cold air.

An Inaccurate Thermostat Setting

Your home may not stay at the desired temperature, or the air coming from the vents may seem somewhat cool even when the fan is on. In these cases, the solution may be a simple one, especially if the thermostat’s setting is causing the problem. Check the thermostat, making sure it’s set to “Auto” instead of “On.” If that doesn’t work, call for help.

A Dirty Air Filter

If the furnace overheats, it may blow cold air. Modern furnaces include safety devices known as limit switches, which turn off the burners when an unsafe temperature is reached. However, the unit’s fan will continue to run, cooling it down and preventing damage.

Most instances of overheating are due to poor airflow, which is usually caused by a clogged air filter. If a replacement filter doesn’t get the warm air flowing again, consider seeking professional advice.

Inadequate Gas or Power Supply

Your home’s furnace may shut down if it’s not getting the power it needs to provide warmed air. If your gas or electrical supply isn’t turned off, there’s likely a problem within the delivery system. These problems are dangerous for DIYers to tackle, so be sure to get professional help.

Clogged Drain Lines

Today’s high-efficiency heating units have drain lines that eliminate the water created during the home-heating process. A clogged condensate drain line will typically trigger a switch that prevents the unit’s burners from coming on. If your unit is blowing cold air, a technician can check the condensate drain lines and remove any clogs.

Get to the Root of the Problem

If you’ve taken the above steps but you’re still getting cold air from the vents, it’s best to contact a heating and air conditioning expert serving St. Louis. At Scott-Lee Heating Company, we offer a full range of heating and cooling repairs and can even assist with air quality issues and metalwork. Call us today to learn more about our products and services.