Arrangement comprising a service port being attachable to a refrigerant line of an air conditioning system, said service port having a circumferential direction and a groove in said circumferential direction formed therein to which a device can be attached, an extension beyond the groove , a collar in said circumferential direction between the groove and the extension and an end , a device for preventing refrigerant leaks in air conditioning system service ports , the device comprising: a coupler to be coupled to the air conditioning system service port , wherein said coupler is a quick coupler having a detent for engaging in the groove formed in the service port ; a main body having a longitudinal direction, an open end and being disposed adjacent said coupler in said longitudinal direction, wherein the end of the port can be inserted into said open end ; a stem movable inside said main body in said longitudinal direction; a sealing element adjacent said stem ; a head fastened to said main body , said head having an internal thread ; and a handle having a shaft with an external thread to be screwed into said internal thread of said head , said shaft having a free end remote from said handle for contacting said stem and pushing said sealing element adjacent said stem against said end of the service port upon turning said handle . a service port being attachable to a refrigerant line of an air conditioning system, said service port having a circumferential direction and a groove in said circumferential direction formed therein to which a device can be attached, an extension beyond the groove , a collar in said circumferential direction between the groove and the extension and an end , a device for preventing refrigerant leaks in air conditioning system service ports , the device comprising: a coupler to be coupled to the air conditioning system service port , wherein said coupler is a quick coupler having a detent for engaging in the groove formed in the service port ; a main body having a longitudinal direction, an open end and being disposed adjacent said coupler in said longitudinal direction, wherein the end of the port can be inserted into said open end ; a stem movable inside said main body in said longitudinal direction; a sealing element adjacent said stem ; a head fastened to said main body , said head having an internal thread ; and a handle having a shaft with an external thread to be screwed into said internal thread of said head , said shaft having a free end remote from said handle for contacting said stem and pushing said sealing element adjacent said stem against said end of the service port upon turning said handle . a coupler to be coupled to the air conditioning system service port , wherein said coupler is a quick coupler having a detent for engaging in the groove formed in the service port ; a main body having a longitudinal direction, an open end and being disposed adjacent said coupler in said longitudinal direction, wherein the end of the port can be inserted into said open end ; a stem movable inside said main body in said longitudinal direction; a sealing element adjacent said stem ; a head fastened to said main body , said head having an internal thread ; and a handle having a shaft with an external thread to be screwed into said internal thread of said head , said shaft having a free end remote from said handle for contacting said stem and pushing said sealing element adjacent said stem against said end of the service port upon turning said handle . <EOS>