Why Your Furnace Blows Cold Air (Common Causes)

If your furnace is blowing cold air, the system may be failing to heat properly—or it may be moving already-cool air through the house. The problem is often tied to airflow issues, a failure in ignition/combustion, or a sensor/thermostat setting that stops (or bypasses) normal heating.

Start with the simplest checks first: confirm the thermostat is set to Heat, and that the temperature is set higher than the current room temperature. Also verify the fan setting isn’t on “On” (which can circulate air without heating). If the thermostat shows the heat is calling but the air never warms, move to the next steps.