Air drying cartridge

The cartridge (13) has an indication unit (40) for automatically presenting information concerning to cartridge types e.g. air dryer type and air conditioning type, in a vehicle. The indication unit is arranged in a recess and/or behind a projection, and a material of a component of the cartridge doped with sensible additive is formed as the indication unit. The indication unit has a contour correlated with the cartridge types, and a radio frequency identification (RFID) element (44) is provided in the indication unit. Independent claims are also included for the following: (1) an air conditioning system comprising an air drying cartridge (2) a method for operating an air drying cartridge.