The refrigerating machine is considered in the paper as a system of closed pipelines of various diameters, which enables the excitation of thermodynamic processes in them by moving working body. The method of the on-site determination of the refrigerating machine efficiency based on the two temperature sensors data processing   has been elaborated and the device for real time testing of refrigerating machine during one cycle of its operation has been created.  Such assessment does not contradict the physical meaning of the concept of efficiency. The developed method and device can be used to indirect determination of  the losses in the refrigerating machine as well as the type of refrigerant  in the system without the need for refrigerating machine unsealing for extraction and laboratory analysis of the refrigerant, which is relevant during refrigerators routine servicing and vitally important for the environmental concerns  solution.