A valve actuator fault analysis system for detecting, analyzing and reporting valve actuator performance characterized as deviations, malfunctions and failures. The fault analysis system includes an expert system that monitors the valve actuator and related components, such as the power supply and signal line, for determining causal factors of degraded and/or defective performance; generation of fault-analysis reports in a readable text format file; and methods for characterizing deviations, malfunctions and failures, for generating and concatenating event messages and for detecting and characterizing events that take place in valve actuators, peripheral systems and devices and displaying the results on a display device. The system can operate either in conjunction with, or be embedded in the hardware of a pneumatic valve positioner, an electrical valve actuator and/or similar devices, and can receive messages from external sources, process them, and produce fault-analysis reports for display to the user.