Compressed air maintenance apparatus, comprising the following components: - an electrically actuated switch-on valve, which has a feed inlet connectable to a compressed air source, a venting outlet connected to the atmosphere and a working outlet, and which can be switched into a working position connecting the working outlet to the feed inlet and into a venting position connecting the working outlet to the venting outlet, - an apparatus outlet, which can be connected to an external user device and which is connected to the working outlet of the switch-on valve via an outlet passage, - a pressure sensor suitable for measuring the outlet pressure prevailing in the outlet passage and/or a flow sensor suitable for measuring the outlet flow in the outlet passage, - and an internal electronic control unit, which is connected in terms of signal technology to the switch-on valve and to the pressure sensor and/or to the flow sensor and which can be operated in a monitoring mode, characterised in that - the switch-on valve has a 3/3-valve functionality and can in addition be switched into a blocking position, in which its working outlet connected to the apparatus outlet is disconnected both from the feed inlet and from the vent outlet, - in that the internal electronic control unit can, in the blocking position and/or in the working position, as an alternative to the monitoring mode be operated in a learning mode, in which, in the blocking position, a time-dependent pressure drop of the outlet pressure and/or, in the working position, a time-dependent flow profile of the outlet flow can be determined and stored in the form of reference information (43, 44) in storage means of the internal electronic control unit, - in that the internal electronic control unit is provided with comparator means, by means of which the actual information supplied in the monitoring mode by the pressure sensor and/or by the flow sensor can be compared to the associated reference information (43, 44), - and in that the internal electronic control unit is provided with outputting means, which can output an electric diagnostic signal as a function of the comparison result of the comparator means. - an electrically actuated switch-on valve, which has a feed inlet connectable to a compressed air source, a venting outlet connected to the atmosphere and a working outlet, and which can be switched into a working position connecting the working outlet to the feed inlet and into a venting position connecting the working outlet to the venting outlet, - an apparatus outlet, which can be connected to an external user device and which is connected to the working outlet of the switch-on valve via an outlet passage, - a pressure sensor suitable for measuring the outlet pressure prevailing in the outlet passage and/or a flow sensor suitable for measuring the outlet flow in the outlet passage, - and an internal electronic control unit, which is connected in terms of signal technology to the switch-on valve and to the pressure sensor and/or to the flow sensor and which can be operated in a monitoring mode, characterised in that - the switch-on valve has a 3/3-valve functionality and can in addition be switched into a blocking position, in which its working outlet connected to the apparatus outlet is disconnected both from the feed inlet and from the vent outlet, - in that the internal electronic control unit can, in the blocking position and/or in the working position, as an alternative to the monitoring mode be operated in a learning mode, in which, in the blocking position, a time-dependent pressure drop of the outlet pressure and/or, in the working position, a time-dependent flow profile of the outlet flow can be determined and stored in the form of reference information (43, 44) in storage means of the internal electronic control unit, - in that the internal electronic control unit is provided with comparator means, by means of which the actual information supplied in the monitoring mode by the pressure sensor and/or by the flow sensor can be compared to the associated reference information (43, 44), - and in that the internal electronic control unit is provided with outputting means, which can output an electric diagnostic signal as a function of the comparison result of the comparator means.