Re: self levelling susp
I dont think there is any wiring with ZF/ Sachs/ Boge (now Mannesman!)Nivomat dampers, its a passive system.
The level control with the Nivomat is carried out at the rear axle and can only be performed while driving because the internal pump is operated by the relative movements between the body and the axle caused by road irregularities. However, the Nivomat does not drop immediately as soon as the vehicle stops but, due to its internal tightness, it can maintain the level reached for a longer period.
The Nivomat pump is operated by the piston rod. When the piston rod is moved out (pull), the pump chamber is expanded. Oil is sucked from the low-pressure reservoir into the pump chamber through the suction tube, the hollow pump rod and the open inlet valve. When the piston rod is moved in (push), the pump chamber is made smaller, the inlet valve closes and the outlet valve opens. Oil is pressed into the working chamber between the exterior side of the control sleeve and the interior side of the piston rod. At the same time, oil is displaced into the high-pressure accumulator through the open side of the cylinder tube. The highpressure gas cushion is increasingly compressed during pumping.
When approaching the intended vehicle level, a spiral groove, located on the pump rod and until then covered by the control sleeve, is opened. The opened groove forms a bypass between the pump chamber and the high-pressure accumulator. Thus, no more oil is sucked out of the low-pressure reservoir; oil is only moved between the pump chamber and the working chamber. When the vehicle is being unloaded while stationary, the piston rod first moves out further since the balance between the Nivomat extension force and the load on the Nivomat is disturbed. This further extension of the piston rod causes a relief bore on the pump rod to be opened. At the level position, this relief bore is
covered by the control sleeve. It allows an oil flow from the high-pressure accumulator into the low-pressure reservoir, which results in a corresponding pressure reduction.
When driving on bumpy roads the Nivomat is excited more than normal. In this case, the Nivomat adjusts to a higher level (15 - 20 mm). This results in the vehicle reaching a greater ground clearance, depending on the ratio of movement between the Nivomat and the wheel