BAS Function In Normal Operation
The BAS brake servo (A7/7) is supplied continuously via the vacuum line with inlet manifold vacuum or pump vacuum on diesel models. If the brake is not actuated, equal vacuum exists on both sides of the diaphragms. The compression spring holds the vacuum piston in its starting position. On brake application, atmospheric air is fed to the back of the diaphragms via a duct. A pressure difference that increases with the braking is created between the front and rear chambers of the servo and resulting force acts in the direction of the master brake cylinder and supplements foot pressure.