A system for airconditioning the passenger compartment of a vehicle

The system (10) comprises a circuit (12) in which a working fluid is subjected to a thermodynamic cycle and a by-pass duct (36) that has one end connected between the compressor (14) and the condenser (16) and the other end connected to the input of the heat exchanger (20). Switching solenoid valves (26,34,19) adopt a first and a second operative condition in which the by-pass duct (36) is excluded from and connected in the circuit (12), respectively, so that, in the first condition, the system (10) operates as a cooling system and the heat exchanger (20) acts as an evaporator and, in the second condition, the system (10) operates as a heating system with a heat pump and the exchanger (20) acts as a condenser. A further heat exchanger (24) is interposed between the heat exchanger (20) and the intake of the compressor (14) and can act, in the first and second operative conditions of the solenoid valves (26,34,19), respectively, as an accumulator for the working fluid in the liquid state, and as an evaporator. The further heat exchanger (24) is connected to the liquid engine-coolant circuit (30) by means of a variable-flow solenoid valve (32).