An automotive air conditioning system comprising a main heating unit 4 for heating air passing through an air conditioning duct 2 with cooling water of an engine E and a refrigeration cycle device 20 having a first refrigerant circulating circuit 21 which is a cooler mode and a second refrigerant circulating circuit 22 which is a heater mode and whose operation is controlled by an ECU 10, wherein while the automotive air conditioning system is operated in a heater mode functioning as auxiliary heating, in the event that a heating load is equal to or larger than a predetermined value, a refrigerant compressor 7 is kept switched off until a predetermined time T.sub.1 has elapsed after the engine E has started.In addition, a heating device is provided on the refrigerant compressor or an accumulator so that the refrigerant compressor or the accumulator is heated by the heating devices while the automotive air conditioning system is operated in the heater mode functioning as auxiliary heating.