A method is disclosed for monitoring the functions of a friction clutch which is arranged in a vehicle between a drive motor and a compressor of a compressed air supply system and which can be disengaged and engaged pneumatically. In a delivery mode of the compressor, at least one operating parameter is detected by sensor and evaluated in an electronic control unit. When a slipping condition of the friction clutch is identified, a value for a cut-off pressure of the compressor stored in the electronic control unit is reduced. When a slipping condition has been identified, the delivery mode of the compressor is ended by disengagement of the friction clutch, and a warning signal and/or warning information is outputted.