COMPRESSED AIR SUPPLY UNIT, COMPRESSED AIR SUPPLY SYSTEM, VEHICLE, AND OPERATING METHOD

A compressed air supply unit includes a main pneumatic line from the compressed air connection to the compressed air supply connection and includes an air dryer arranged in the main pneumatic line for drying the compressed air. A branching line branches off from the main pneumatic line between the compressed air connection and the air dryer and reconnects to the main pneumatic line between the air dryer and the compressed air supply connection. A main line switch valve is arranged upstream of the branching line between the compressed air connection and the air dryer and blocks the main pneumatic line in a first operating mode. A method is for operating a compressed air supply system. A vehicle and/or a compressed air supply system have a compressed air supply unit.