The answer to 'heat pump blowing cold air' is that there are several common causes, including a refrigerant leak, a malfunctioning reversing valve, or a problem with the compressor. Symptoms may include the heat pump blowing cold air even when set to 'heat' mode, the system short-cycling, or the compressor not turning on.
In many cases, the solution may require the expertise of a professional HVAC technician. Attempting to diagnose and repair a heat pump issue without the proper training and equipment can be dangerous and may even void the warranty. However, there are some basic troubleshooting steps a homeowner can try, such as checking the thermostat settings, cleaning the air filters, and ensuring the outdoor unit is free of debris.