A motor vehicle air conditioning system with an electric heating device, in particular PTC heating device, comprising - at least two electric heating elements, in particular PTC heating elements, for heating the air directed through the motor vehicle air conditioning system, - at least two conductive elements, which are in electric communication with the at least two electric heating elements, for supplying the at least two electric heating elements with electric current and - one frame on or in which the at least two electric heating elements and the at least two conductive elements are arranged, - at least two modules, each having two heat conducting lamella units with a plurality of heat conducting lamellas, wherein at least one electric heating element and at least four conductive elements are arranged in each of the at least two modules and the at least two modules can be mechanically and/or electrically connected by means of at least one connection means, thereby enabling the production of different sizes and/or heat outputs of the electric heating device due to an arrangement of a differing number of modules, wherein the at least two modules are identical and the at least one connection means is arranged on the conductive elements, characterised in that two contact plates are positioned on the side of the two heat conducting lamella units facing away from the electric heating element, and the conductive elements are designed as contact plates or as area elements, and in that the conductive elements formed as area elements can be connected in a common plane of the area elements by means of the at least one connection means, thereby enabling the production of different lengths of the electric heating device. - at least two electric heating elements, in particular PTC heating elements, for heating the air directed through the motor vehicle air conditioning system, - at least two conductive elements, which are in electric communication with the at least two electric heating elements, for supplying the at least two electric heating elements with electric current and - one frame on or in which the at least two electric heating elements and the at least two conductive elements are arranged, - at least two modules, each having two heat conducting lamella units with a plurality of heat conducting lamellas, wherein at least one electric heating element and at least four conductive elements are arranged in each of the at least two modules and the at least two modules can be mechanically and/or electrically connected by means of at least one connection means, thereby enabling the production of different sizes and/or heat outputs of the electric heating device due to an arrangement of a differing number of modules, wherein the at least two modules are identical and the at least one connection means is arranged on the conductive elements, characterised in that two contact plates are positioned on the side of the two heat conducting lamella units facing away from the electric heating element, and the conductive elements are designed as contact plates or as area elements, and in that the conductive elements formed as area elements can be connected in a common plane of the area elements by means of the at least one connection means, thereby enabling the production of different lengths of the electric heating device.