The answer to 'why is my ductless system blowing cold air' is that there could be several common causes, such as a refrigerant leak, a faulty compressor, or an issue with the thermostat. Ductless systems, also known as mini-splits, use refrigerant to absorb heat from the indoor air and expel it outside, so any problems with the refrigerant flow or compressor can lead to the system blowing cold air even when it's not supposed to.
Other potential causes include a dirty air filter, a malfunctioning reversing valve, or a problem with the indoor or outdoor unit. If the system is blowing cold air constantly, it's likely a more serious issue that requires professional diagnosis and repair. However, some simpler problems like a dirty air filter can be addressed by the homeowner.