The answer to 'why is my HVAC system blowing hot air' is that there could be several common causes, such as a refrigerant leak, a problem with the compressor, or a thermostat issue. Symptoms may include the air coming out of the vents feeling warm instead of cool, and the system may not be able to effectively lower the temperature in your home.
Some potential solutions include checking the thermostat settings, inspecting the air filters, and ensuring the outdoor unit is not obstructed. However, if the issue persists, it's best to call a professional HVAC technician to diagnose and repair the problem, as they have the expertise and tools to properly identify and fix the underlying issue.