Vehicle air conditioner having refrigerant cycle with heating function

An air conditioner for a vehicle, comprising:

• an air conditioning case defining an air passage through which air flows into a passenger compartment of the vehicle;
• a refrigerant cycle system including a compressor for compressing refrigerant, an exterior heat exchanger disposed outside the air conditioning case, a pressure reducing device for decompressing refrigerant, an interior heat exchanger disposed inside the air conditioning case and a hot gas bypass passage through which refrigerant discharged from the compressor is directly introduced into the interior heat exchanger while bypassing the exterior heat exchanger, the refrigerant cycle system being constructed to switch a cooling refrigerant cycle where refrigerant discharged from the compressor is returned to the compressor through the exterior heat exchanger, the pressure reducing device and the interior heat exchanger, and a hot gas heater cycle where the refrigerant discharged from the compressor is directly introduced to the interior heat exchanger through the hot gas bypass passage;
• and
• a control unit for controlling operation of the refrigerant cycle system to set a cooling mode for cooling air in the interior heat exchanger by using the cooling refrigerant cycle, and a heating mode for heating air in the interior heat exchanger by using the hot gas heater cycle, wherein:
• the control unit includes
• determining means for determining whether a quantity of retained water is in the interior heat exchanger, and
• control means for controlling temperature of air blown out of the interior heat exchanger to a range lower than a dew point even when air blown out of the air conditioning case is cooled by a vehicle windshield when the determining means determines that the quantity of retained water is in the interior heat exchanger in the heating mode.