An automotive air conditioning system comprising: • an air cooling circuit including a compressor, a condenser, an expansion valve and an evaporator, fluidically connected to be flowed through, during operation, by a heat transfer fluid, and a blower fan associated with the evaporator and operable to generate an airflow through the evaporator; • an air heating circuit including a liquid/air heater configured to be flowed through, during operation, by a heat transfer fluid, and arranged close to the evaporator to be also flowed through by the airflow generated by the blower fan associated with the evaporator, and a flow rate regulation solenoid valve arranged to regulate the flow rate of the heat transfer fluid through the heater; and • an electronic control unit configured to receive a measured evaporator air temperature (T EVAP) and a set cabin air temperature (T CSP) and to switch an operating condition of the compressor when the measured evaporator air temperature (T EVAP) exhibits a given relation with at least one on/off threshold temperature (T T) computed, in at least certain operating conditions, based on the set cabin air temperature (T CSP); wherein the electronic control unit is further configured to: • receive a measured cabin air temperature (T CAB), a measured external air temperature (T EXT) and a measured outlet air temperature (T OUT); • compute a cabin air temperature error based on the set and measured cabin air temperatures (T CSP, T CAB); • generate a control signal based on the cabin air temperature error by implementing a proportional-integral-derivative regulator; • compute a target outlet air temperature (T OSP) based on the control signal; and • generate an electrical on/off command signal for the compressor of the air cooling circuit and an electrical regulating command for the flow rate regulation solenoid valve of the air heating circuit based on the set cabin air temperature (T CSP), the target and measured outlet air temperatures (T OSP, T OUT), the measured external air temperature (T EXT) and the measured evaporator air temperature (T EVAP). • an air cooling circuit including a compressor, a condenser, an expansion valve and an evaporator, fluidically connected to be flowed through, during operation, by a heat transfer fluid, and a blower fan associated with the evaporator and operable to generate an airflow through the evaporator; • an air heating circuit including a liquid/air heater configured to be flowed through, during operation, by a heat transfer fluid, and arranged close to the evaporator to be also flowed through by the airflow generated by the blower fan associated with the evaporator, and a flow rate regulation solenoid valve arranged to regulate the flow rate of the heat transfer fluid through the heater; and • an electronic control unit configured to receive a measured evaporator air temperature (T EVAP) and a set cabin air temperature (T CSP) and to switch an operating condition of the compressor when the measured evaporator air temperature (T EVAP) exhibits a given relation with at least one on/off threshold temperature (T T) computed, in at least certain operating conditions, based on the set cabin air temperature (T CSP); • receive a measured cabin air temperature (T CAB), a measured external air temperature (T EXT) and a measured outlet air temperature (T OUT); • compute a cabin air temperature error based on the set and measured cabin air temperatures (T CSP, T CAB); • generate a control signal based on the cabin air temperature error by implementing a proportional-integral-derivative regulator; • compute a target outlet air temperature (T OSP) based on the control signal; and • generate an electrical on/off command signal for the compressor of the air cooling circuit and an electrical regulating command for the flow rate regulation solenoid valve of the air heating circuit based on the set cabin air temperature (T CSP), the target and measured outlet air temperatures (T OSP, T OUT), the measured external air temperature (T EXT) and the measured evaporator air temperature (T EVAP).