Vehicular air-conditioning system

A vehicular air-conditioning system (10) has a heat pump circulation passage (18) for circulating a coolant with a compressor (16), To the heat pump circulation passage (18), there are connected a condenser (20) for performing a heat exchange between a coolant and ambient air, an expansion valve (22), a first evaporator (24), a heater (26), and a second evaporator (30). The heat pump circulation passage (18) includes a coolant retrieval passage (44) extending from a divider (42) between the condenser (20) and the gas-liquid separator (34) and connected to the compressor (16). A second backflow check valve (32b) for preventing the coolant from flowing from the compressor (16) to the divider (42) and a solenoid-operated valve (38c) are connected to the coolant retrieval passage (44).