Why is my furnace blowing out cold air?

Have you ever gone to turn on your furnace only to discover that instead of warming up your home as expected, it starts blowing out lukewarm or even cold air? You know there is a problem, but what it is, exactly, can vary depending on the situation.

Here are a few common issues that can lead to the faulty functioning of your furnace.

1. Thermostat

If your thermostat is set to “Fan” instead of “Auto,” your furnace’s air handler will automatically blow un-heated air into the room, even with your furnace in a heating cycle.  By switching the setting, you may find a quick and easy solution to your problem.

2. Limit switch

If your furnace has a sensory switch that dictates when the unit will blow out cold or hot air, the switch can get broken or stuck. Then, the fan will not receive a signal to turn off even when the room reaches a certain temperature. Instead, the fan will continue running even after the furnace’s heating cycle is completed. Without the burners ignited, the air will be consistently cold.

3. Air Filter

Another common cause for sustained cold air is a dirty filter, which can cause your furnace to overheat. When your furnace overheats from being overworked, the fan often is programmed to switch on automatically and cool down the system as a safety measure. Industry professional suggest replacing a dirty filter as soon as possible, as continuing to run the system can slowly degrade the furnace’s heat exchanger. You can find replacement products for your furnace from suppliers, such as McCall’s Supply.

4. Flame sensor

Flame sensors, which also are safety devices, test whether a furnace’s burners are lit. If a sensor gets dirty, it will turn off the burners prematurely. This leaves your furnace without a heat source, resulting in the cold air. The professionals at McCall’s are trained to professionally clean dirty flame sensors and get them working properly.

5. Pilot Light

For older gas models, the small pilot light, which is designed to burn constantly to ignite gas from a valve, may be the culprit. If the pilot light is extinguished, the accompanying thermocouple will cool down, and the electromagnetic gas valve will close. Your unit’s instruction manual may be able to guide you in re-lighting the pilot light, or a professional can help.

Other common causes for cold air coming out of your furnace include an empty oil tank or dirty oil; various thermostat problems; issues with computerized controls; a faulty thermocouple; or leaking ducts, among others. If you’re unsure what is the problem or you need help fixing it, contact a McCall’s Supply dealer near you. With 18 locations spread throughout South Carolina, the company prides itself on accessibility for customers who want to deal with a representative in-person, by phone or online.