The HVAC Unit has a heater that heats the air using the heat from the engine coolant and an evaporator that cools the air through the evaporation of the refrigerant (A/C gas). It creates a temperature environment for the cabin following the operation of the instrument panel. Another important function is to defog the window by utilizing the characteristic of humidity reduction by cooling the air. Current air conditioner for automobile first cools down the air to a lot lower temperature than what was set by the user so that the window does not get foggy as much as possible. Then part of the cooled air goes through the heater to be warmed up to control to be at the set temperature. By using a humidity sensor, the temperature that is tentatively cooled down to is optimized, enabling a large reduction in operating rate of the compressor. Similarly, the reduction in the operating rate of the compressor for conservation is realized through the use of the linear angle internal / external air damper which can freely set the amount of ambient air introduction.