If your heater is blowing cold air. Find relief for the present and future. Once you know how to troubleshoot your furnace not blowing hot air, why it happens, and how to keep it from happening again, you’ll never be in this situation again.

Why is my heater blowing cold air?

Dirty Air Filter Cause Heaters to Blow Cold Air

An air filter is an essential piece of an HVAC system. When these are clean, these filters provide clean, fresh air for your home. However, when they’re dirty, your comfort could be in jeopardy. In fact, a dirty air filter can lead to a heater blowing cold air.

When this filter is too dirty, it blocks airflow over the furnace’s heat exchanger. This can cause the system to overheat, which trips a high limit switch—leading to a unit shutdown. This is a safety measure to prevent a fire or further complications.

Thermostat Not Working

Since your thermostat communicates your home’s temperature needs to the furnace, if it isn’t working correctly, your furnace could blow cold air because it isn’t receiving the proper instructions from your thermostat.

Replacing your thermostat ensures accurate communication with your furnace to stop cold air issues. Have your thermostat replaced by your HVAC technician, and consider upgrading to a programmable or smart thermostat for better control over indoor comfort and energy consumption.

The pilot light is out

A pilot light is a small gas light that burns continuously to ignite a larger burner, such as a furnace. However, this light can be extinguished if there is a draft, a dirty valve, or a faulty thermocouple (a safety device that shuts off gas when no pilot light is detected). Look for a pilot light on models that are 20 or more years old; newer models do not typically have this feature. To fix this pilot light issue, you’ll need to use a lighter to reignite the flame. While you can handle this yourself, choosing a professional may be the best decision. This will ensure everything is done professionally. Once the pilot light is lit, the system should be ready to create that warm air!

The system has overheated 

When a furnace only blows cold air, there’s a chance the heater could have overheated. But don’t worry, this usually doesn’t mean the unit is broken. When the system overheats, there’s a safety feature that shuts the system off. This is a good thing—it could prevent a fire, carbon monoxide leak, or even an explosion.

Even if the furnace’s safety switch powers off the unit, it may temporarily blow cold air. However, the entire system will eventually turn off.