a wall unit forms a part of the outer wall of a vehicle cab . in order to simplify the accommodation of electrical components in the vehicle cab and to reduce the cost of wiring , the wall unit is configured as a pre - assembled module , which includes a support structure on which electrical components , such as vehicle function controllers , fuses and relays , are fastened . the electrical components are at least partially covered by enclosure elements . the electrical components can be electrically connected with corresponding vehicle component groups via connectors .