If the vehicle has the refrigerant cycle system with indoor heat exchanger in the HVAC, it is possible heating and cooling by changing refrigerant flow. A heat pump cycle system can be divided into two large, it is possible to A / C cycle, mainly used during the cooling, but it is possible to Heat Pump cycle, mainly used during the heating. This system is new technology and is very difficult to control and supplying constant heating energy into the cabin. And if the outside temperature is higher, air-conditioning load is increased and the potential failure possibility of Electric Compressor also is increased. And Electric Compressor operating noise is also growing, so user complains this noise. In addition, control is required to achieve optimal thermal comfort, with minimal power consumption for air conditioning. I want to study heat pump system that minimizes heat pump operating noise, determination of lower power consumption cycle.