Maintenance apparatus for charging and discharging carbon dioxide into/from an air conditioning system mounted on a motor vehicle; said maintenance apparatus comprising: at least two external ducts, which are structured to be connected to said air conditioning system and are designed to be passed through, during a discharging operation or a charging operation of said air conditioning system, by a flow of carbon dioxide having a first pressure and a first flow rate; a tank containing carbon dioxide; a charging unit, which is designed to hydraulically connect said tank of carbon dioxide to said ducts to charge, during the charging operation, a given amount of carbon dioxide into said air conditioning system; a discharging circuit, which is provided with a discharging duct and is designed to be hydraulically connected to said ducts to receive the carbon dioxide contained in the air conditioning system; the discharging circuit is further structured so as to discharge the carbon dioxide received into the environment through said discharging duct; said maintenance apparatus further comprising: pressure and flow rate reduction means, which are arranged along said discharging duct and are structured so as to reduce the first pressure and the first flow rate of the carbon dioxide to a second predetermined pressure and, respectively, to a second predetermined flow rate; an electronic measuring apparatus, which is arranged along said discharging duct downstream of the pressure and flow rate reduction means and is configured so as to provide an electric signal indicating the amount of carbon dioxide that passes through said discharging duct; electronic control means, which are configured so as to determine the amount of carbon dioxide discharged from the air conditioning system, through said discharging duct, into the environment based on said electric signal. at least two external ducts, which are structured to be connected to said air conditioning system and are designed to be passed through, during a discharging operation or a charging operation of said air conditioning system, by a flow of carbon dioxide having a first pressure and a first flow rate; a tank containing carbon dioxide; a charging unit, which is designed to hydraulically connect said tank of carbon dioxide to said ducts to charge, during the charging operation, a given amount of carbon dioxide into said air conditioning system; a discharging circuit, which is provided with a discharging duct and is designed to be hydraulically connected to said ducts to receive the carbon dioxide contained in the air conditioning system; the discharging circuit is further structured so as to discharge the carbon dioxide received into the environment through said discharging duct; said maintenance apparatus further comprising: pressure and flow rate reduction means, which are arranged along said discharging duct and are structured so as to reduce the first pressure and the first flow rate of the carbon dioxide to a second predetermined pressure and, respectively, to a second predetermined flow rate; an electronic measuring apparatus, which is arranged along said discharging duct downstream of the pressure and flow rate reduction means and is configured so as to provide an electric signal indicating the amount of carbon dioxide that passes through said discharging duct; electronic control means, which are configured so as to determine the amount of carbon dioxide discharged from the air conditioning system, through said discharging duct, into the environment based on said electric signal. pressure and flow rate reduction means, which are arranged along said discharging duct and are structured so as to reduce the first pressure and the first flow rate of the carbon dioxide to a second predetermined pressure and, respectively, to a second predetermined flow rate; an electronic measuring apparatus, which is arranged along said discharging duct downstream of the pressure and flow rate reduction means and is configured so as to provide an electric signal indicating the amount of carbon dioxide that passes through said discharging duct; electronic control means, which are configured so as to determine the amount of carbon dioxide discharged from the air conditioning system, through said discharging duct, into the environment based on said electric signal.