Why is My Furnace Blowing Cold Air?

TechXpert verified by Ken Kontra

There are several issues that can cause your furnace to blow cold air, ranging from an incorrect thermostat setting to a system malfunction. Some underlying problems are more complicated than others, but you can get to the bottom of your furnace issue with a bit of close inspection and a list of potential problems to watch for.

Reasons for Cold Airflow

If your furnace is blowing cold air, the reason could be as simple as an incorrect thermostat setting. Other explanations could be a bit more complex or difficult to determine, like leaking air ducts. Either way, it’s important to consider all the possibilities before jumping to conclusions.

Here’s a rundown of why your furnace may be blowing cold air:

Incorrect thermostat setting
Empty oil tank or propane tank
Furnace is overheating due to insufficient airflow or overfiring
Extinguished pilot light
Valve issues
Clogged oil filters (if you have an oil-fired furnace)
Faulty thermocouple
Faulty electronic ignition
Dirty flame sensor
Gas or oil burner malfunction

It can take time, effort, and know-how to investigate all of these issues, so if you’re not too familiar with the parts and processes of your furnace, turn to a professional for some help.

You won’t want to leave it too long, since faulty parts can lead to bigger issues before you know it, but the good news is an expert can get things back on track quickly.