An automatic steam car washing system is provided. The support member may be formed from an anodized electrically conductive support material and generally has nonconductive surfaces in contact with the valve and the liner. The backplane further includes a monitoring device operable to determine, for each connected peripheral, whether a peripheral is compatible with the connected control apparatus and, if the peripheral is incompatible, the monitoring device activates the respective optical signaling device assigned to the slot for the incompatible peripheral. A cover cap extends over the valve cover and is fixed with an attachment shoulder on the base body.