The answer to 'why is my mini split blowing cold air' is that there could be several common causes, such as a refrigerant leak, a malfunctioning compressor, or a problem with the thermostat or control system. Symptoms may include the unit running constantly, insufficient cooling, or the air coming out much colder than expected.
If the issue is a refrigerant leak, you may need to have a professional technician diagnose and repair the leak, then recharge the refrigerant to the proper level. A compressor failure or control system problem will likely require professional service as well. However, some simpler issues like a dirty air filter or incorrect thermostat settings can sometimes be fixed by the homeowner.