3 Reasons Why Your Furnace Blows Cold Air

24 January 2022
 Categories: , Blog


Your furnace provides heat throughout your home when cold weather strikes. So, when it gives off cold air when you power it up, that's a huge red flag. You should call a heating repair expert immediately before the problem escalates. 

Here are some reasons your furnace blows cold air and what you can do about it. 

Dirty Air Filter

An air filter blocks off contaminants in your indoor air. When the filters are clean, fresh air is a guarantee in your home. However, dust, soot, or grime can clog the air filter and impede proper airflow.

As a result, your furnace works extra hard to heat your home. The added strain causes it to overheat and trigger the high limit switch as a safety measure. Oftentimes, the furnace blows some cold air into your home for some time before it turns off. 

To resolve cold air issues due to a dirty air filter, replace the filter with a new one, preferably every three months. However, if you have allergies or pets in your home, you should replace the filter more often to avoid additional problems. 

Thermostat Issues

A faulty or incorrectly set thermostat is another likely cause of cold air from your furnace. For instance, if your furnace has been off for months, your furnace may blow cold air if it's still on the cold air setting.

When your thermostat setting reads "ON', the furnace fan will blow even when your furnace system is off. To restore your unit's functionality, you should reset your thermostat to the 'auto' channel to ensure your furnace only runs after activation of the heating cycle. 

A wiring issue can also cause your furnace to malfunction, especially if you installed the thermostat yourself. In addition, a thermostat that isn't compatible with your furnace may also cause cold air problems. Reach out to a heating repair technician for assistance if you suspect thermostat issues with your system. 

Damaged Ductwork

Ducts supply heated air into your home. If the air ducts develop cracks or holes, cold air from your attic or crawlspace may find its way inside them and end up in your home. Also, hot air from your heater may escape through the cracks in your ductwork. Luckily, a professional can seal the cracks or replace severely damaged ductwork. 

Additionally, incorrectly sized ductwork can affect your furnace's efficiency. If you have undersized ductwork, less air flows through the ducts, and your furnace will blow cold air. 

Thankfully, you can avoid these furnace problems if you keep up with preventative maintenance. This way, you will catch issues early before your furnace fails.