In the article, the problems of selected failures that may occur during operation of positive displacement compressors and possible reasons for their occurrence were described. It also included methods for checking performance and diagnostics, with particular emphasis on research using an electronic indicator. Possible mechanical damages of air compressors for various applications have also been characterized. Non-destructive diagnostic methods were described to detect and diagnose damage, taking into account their suitability and limitations in their application. In the further part of the article selected tests results of air compressor, specially adapted to simulation of failures were presented. The test stand has been equipped with sensors for measuring the pressure and temperature of the compressed gas and the sensor of the angular position of the compressor shaft, allowing examining the impact of damage on compressor working parameters. The result of the research was to compare the compressor indicator diagrams in the operational condition, with the simulated failure, and between different failures and to learn the changes of processes taking place inside the cylinder during the compressor’s work cycle. All the test results could be observed in real time, besides the diagnostic software, supporting the tests, made it possible to record measurements. In the described software, it is possible to compare the courses for different cases, to then make a comparative analysis of the results obtained in the state of functional and simulated disability.