The answer to 'why is my furnace blowing cold air' is that there could be several common causes, such as a malfunctioning thermostat, a problem with the furnace's heating element, or issues with the airflow. Some key symptoms include the furnace running but not heating the air, the air coming out feeling cool or lukewarm, and the home not reaching the desired temperature.
The solutions can vary depending on the root cause. For a thermostat issue, you may be able to simply replace the batteries or recalibrate the thermostat. For a problem with the heating element, you may need to have a professional HVAC technician inspect and potentially replace the part. And if the issue is with airflow, the technician can check for blockages in the ductwork or issues with the blower fan. In many cases, it's best to call in a professional HVAC technician to properly diagnose and fix the problem, especially if you're not comfortable working on the furnace yourself.