Description

Power Steering Control Module

The Servotronic unit is speed dependent and is triggered by the electronic speedometer. It is entirely independent of the engine speed:
^ A microprocessor evaluates the speed signal and decides the amount of hydraulic power assistance required. This in turn determines the amount of driver effort required.
^ The power value is transmitted as impulses to the rotary spool steering valve, via an electro-hydraulic converter.
^ The degree of assistance is proportional to the road speed. This means that minimum driver effort is required at parking speed.
^ As the road speed increases, the steering characteristics become more direct, enabling precise and responsive reactions to steering movements.

^ As described above, the control of the valve is by varying the current which is applied to it. The current signal is provided by the Control Module which inputs a vehicle speed signal from the Instrument Cluster.
^ The microprocessor and associated algorithm within the module, provides maximum output current (854 mA) when the vehicle is stationary - the valve will be held closed, providing very easy steering. The current progressively decreases towards zero (15 mA) as the frequency of the speed signal from the Instrument Cluster increases - the valve will be opening in stages. Consequently, an increasing amount of hydraulic pressure is applied to the reaction piston, which increases the feel to the driver.