An air conditioning system for motor-vehicles comprises a thermally controlled expansion valve unit (TXV) for regulating the expansion of the fluid upstream of the evaporator (5), depending upon the temperature downstream of the evaporator (5). The system further includes an intermediate heat exchanger IHX (9) for providing a heat exchange between the conduit (6) upstream of the evaporator (5) and the conduit (7) downstream of the evaporator (5). The thermally controlled expansion valve unit (TXV) is arranged in such a way that its temperature sensor detects the temperature of the fluid along the conduit (7) downstream of the evaporator (5) at a portion of this conduit which is located downstream also with respect to the intermediate heat exchanger IHX (9). In one embodiment, between the evaporator (5) and the thermally controlled expansion valve unit (TXV) there is interposed a connecting flange (10) which enables a conventional system to be easily modified into a system according to the invention. This flange can be integrated with the unit TXV.
