What to do When your Furnace is Blowing Cold Air

Thankfully we did not have an issue with the furnace until the weather warmed up a bit. It even worked fine after we got the basement dry from the flood. Then suddenly it would keep blowing cold air.

Not a good thing for a home with children and a late-running winter. Last week I got sick of flipping the switch manually to make it run properly.

Clearly, I was wrong and it could not wait till later to deal with. More snow is on the way. So I did what I often do when something goes wrong in our house. I ran to Google. What to do when your furnace blows cold air?

To my surprise, it was a rather easy fix. We knew the furnace was working properly. The fan would fire up, the glow plug would come to a glow and ignite the gas. Heat would blow out and the house would warm only for it to get cold again by morning when we need the heat the most.

Two things had been an issue. First, the thermostat had been switched from auto fan to on. Most likely due to a child fiddling. This, of course, caused the fan to keep running even when the furnace was off pushing out cold air.

Then we discovered that the airflow was being blocked. The new filter had quickly filled due to the contaminants in the basement as we scrubbed and cleaned for weeks after the flood. So we pulled it out just enough to test the airflow.

The blocked airflow caused the furnace to overheat and error out. So a quick order of a new filter from Filter Easy and the furnace is running good as new again. Just in time for the cold to return.