The answer to 'why is my heat pump blowing cold air' is that there could be several common causes, such as a problem with the reversing valve, a refrigerant leak, or issues with the compressor. Some key symptoms to look for are the heat pump blowing cool air even when set to 'heat' mode, and the outdoor unit not running.
If your heat pump is blowing cold air, it's important to troubleshoot the issue promptly. While some minor problems can be DIY-fixed, it's generally best to call in a professional HVAC technician to diagnose and repair the issue. Attempting complex repairs on your own could make the problem worse or even create safety hazards.