Systems and methods of the invention relate to diagnosing a compressor. A method may include monitoring a pressure of compressed air within a reservoir of a compressor, actuating an unloader valve of the compressor, and detecting a leak condition of the compressor through recognition of a change in the monitored pressure of the compressed air within the reservoir during a time period in which the unloader valve is actuated. A system is also disclosed including an engine, a compressor operatively connected to the engine, and a controller that is operable to determine a condition of the compressor.