The answer to 'replacement blowing cold air' is that the most common causes are a refrigerant leak, a faulty compressor, or an issue with the air handler. Symptoms may include the air blowing cold but not cooling the home effectively, or the system cycling on and off frequently. Solutions can range from a simple refrigerant recharge to replacing major components like the compressor or air handler.
In many cases, the issue is not something a homeowner can easily diagnose or repair on their own. Attempting DIY repairs on an HVAC system can be dangerous and may even void the warranty. It's generally best to call in a licensed, professional HVAC technician to properly inspect the system and make any necessary repairs.