Return and ventilation valve for a washing unit used for vehicle windows

The system has a check and ventilation valve (11) arranged in a liquid connection, and delivering a cleaning and washing liquid i.e. water, to a nozzle outlet during activation of the system. A part of the liquid connection is provided between the nozzle outlet and the valve and deaerated for draining during non-activation of the system. The valve, and a section (10.1) of a hose assembly (10) connecting the valve with a cleaning and washing liquid source (7) for cleaning and washing liquid are heated and/or accommodated in a heated area (12) of a motor vehicle (2).