When your furnace blows cold air, that issue should be resolved as soon as possible. Especially in the winter! Don’t spend your winter shivering when you could be comfortable. Here are some reasons why your furnace might be blowing cold air:
Pilot Light Isn’t Working
Your furnace could also be blowing cold air if the pilot lights aren’t lit. The pilot light is a small flame that lights a large burner. If the pilot light isn’t lit the furnace won’t heat up.The pilot light could be dirty and need cleaning, or the thermocouple(the copper rod that the pilot light hits) could need to be replaced.
Dirty Air Filter
The filter in your furnace should be changed every 90 days. Dirty filters restrict airflow, which actually causes a safety problem.
Your furnace can overheat when outbound airflow is restricted. A safety control will shut off the burners. That’s why it’s extremely important to change your filters on a regular basis.
Your furnace needs enough gas to work properly. If your furnace doesn’t get enough gas, it won’t blow hot air. Why wouldn’t your furnace get enough gas?
Your gas supply might be turned off. It’s also possible that there’s something in the line that’s preventing the gas from flowing through it. A trained professional should be able to figure out the cause of the problem.
If your blower is on all the time and your furnace is sometimes blowing cold air, the problem likely stems from your thermostat. When your thermostat is set to “on” your blower runs even when your furnace isn’t heating the air. Instead, set your thermostat to “auto”.