During the winter, there is no greater comfort than sitting in front of your furnace and enjoying the heat. But what if you sit in front of the furnace and you notice the furnace blowing cold air? Unthinkable right?
Well, at times you might find that your furnace blowing cold air instead of warm air. This can be due to several reasons. We have listed some of them below.

There might be something wrong with the thermostat.

Check the setting on your thermostat.

If you happen to see that the thermostat fan is ON, then that might be your problem. When the settling is at ON, the furnace blower runs, even if the furnace is not heating the air. This might be the reason why your furnace is blowing cold air.

If this is the problem, you can simply switch the settling to AUTO.

Dirty air filter
Air filters are quite important when it comes to proper airflow. Blocked air filters can restrict the air flow causing the furnace to overheat. In such a situation, the furnace will automatically switch off in order to prevent any damage.

Check your air filters and make sure to change them if they are dirty.

Insufficient gas supply
If the gas supply to the furnace is inadequate, you will find that your furnace is blowing cold air instead of warm air. Check if the gas supply is sufficient or if it has been turned off.

Leaks in ducts
Leaky air ducts can tamper with the proper functioning of the furnace and cause it to give out cold air. The cold air from places like the attic might get through the holes in the ducts causing your furnace to stop giving warm air. Always keep a look out for holes, leaks, and other defects on the ducts of the furnace.