The answer to 'HVAC system blowing cold air' is that your HVAC system could be blowing cold air due to a few common issues. This could be caused by a thermostat malfunction, a refrigerant leak, a problem with the compressor, or a frozen evaporator coil. Symptoms may include inconsistent temperatures, rapid cycling of the system, and high energy bills.
If the system is blowing consistently cold air, it's best to call a professional HVAC technician to diagnose and repair the problem. Attempting DIY repairs on an HVAC system can be dangerous and may void the warranty. A qualified technician will be able to properly inspect the system, identify the root cause, and make the necessary repairs to restore proper heating and cooling.