The air conditioning of our car allows us to travel in the cool even with very high external temperatures, but also allows to quickly remove the internal fogging of the windscreen during the winter, by controlling the humidity of the passenger compartment. The system consists of a compressor and exchanger unit equipped with a sealed circuit inside which there is a special gas. In many cars the compressor is driven by the drive belt of the engine and in other cars it is driven separately. After a more or less long period of use, the air conditioning system may present some problems ranging from the most trivial, such as bad-smelling air, to the more serious, such as failure. In any case, even in the absence of negative signals, it is advisable to carry out maintenance on the car air conditioning to ensure the system works properly. Various car manufacturers recommend carrying out this maintenance once a year or every 15/20,000 kilometres.