System for the diagnosis and monitoring of air supply systems, comprising: a compressor configured to provide compressed air, an air drier configured to extract moisture from the compressed air in the system, characterised in that the system further comprises: at least two sensors, wherein one sensor is configured and arranged so as to sense a status signal of a component to be monitored, and another sensor is configured and arranged so as to sense a reference signal relating to the component to be monitored, an evaluation unit configured to evaluate the signals of the sensors by comparisons between the status signal and the reference signal, wherein the evaluation unit is also configured to convert the sensor signals, using an evaluation logic, into maintenance and/or control signals which control the method of operation of the air supply installation, and wherein the sensors are configured and arranged to determine the temperature at the cooling air inlet as a reference signal and a component temperature or an oil temperature as a status signal and/or the temperature of the air at the process inlet as a reference signal and the component temperature or the oil temperature as a status signal and/or the intake pressure as a reference signal and the intermediate pressure or the final pressure as a status signal and/or the air temperature as a reference signal and the pressure dew point as a status signal on the basis of the measured values relating to the air humidity and the temperature of the air in the compressor. a compressor configured to provide compressed air, an air drier configured to extract moisture from the compressed air in the system, characterised in that the system further comprises: at least two sensors, wherein one sensor is configured and arranged so as to sense a status signal of a component to be monitored, and another sensor is configured and arranged so as to sense a reference signal relating to the component to be monitored, an evaluation unit configured to evaluate the signals of the sensors by comparisons between the status signal and the reference signal, wherein the evaluation unit is also configured to convert the sensor signals, using an evaluation logic, into maintenance and/or control signals which control the method of operation of the air supply installation, and wherein the sensors are configured and arranged to determine the temperature at the cooling air inlet as a reference signal and a component temperature or an oil temperature as a status signal and/or the temperature of the air at the process inlet as a reference signal and the component temperature or the oil temperature as a status signal and/or the intake pressure as a reference signal and the intermediate pressure or the final pressure as a status signal and/or the air temperature as a reference signal and the pressure dew point as a status signal on the basis of the measured values relating to the air humidity and the temperature of the air in the compressor. at least two sensors, wherein one sensor is configured and arranged so as to sense a status signal of a component to be monitored, and another sensor is configured and arranged so as to sense a reference signal relating to the component to be monitored, an evaluation unit configured to evaluate the signals of the sensors by comparisons between the status signal and the reference signal, wherein the evaluation unit is also configured to convert the sensor signals, using an evaluation logic, into maintenance and/or control signals which control the method of operation of the air supply installation, and wherein the sensors are configured and arranged to determine the temperature at the cooling air inlet as a reference signal and a component temperature or an oil temperature as a status signal and/or the temperature of the air at the process inlet as a reference signal and the component temperature or the oil temperature as a status signal and/or the intake pressure as a reference signal and the intermediate pressure or the final pressure as a status signal and/or the air temperature as a reference signal and the pressure dew point as a status signal on the basis of the measured values relating to the air humidity and the temperature of the air in the compressor.