Hydraulic valves
On the hydraulic unit, located in the torsion box behind the rear seat, there is a pump block and valve block. Four electromagnetic hydraulic valves are fitted in the valve block and the function of the valves is to direct the oil flow to the main sequence hydraulic cylinders as well as the fifth bow hydraulic cylinders. The valve has three connections, oil pressure in from the pump, oil pressure to the hydraulic cylinder and return oil to the reservoir. The valve has two positions, active and resting. When the valve is active, pressure in from the pump is connected to pressure to the hydraulic cylinder, and when the valve is resting pressure to the cylinder is connected to the return line to reservoir.
The control section of the valve contains an integrated circuit and a transistor that grounds the coil when the valve is activated. +54 is supplied to the coil and activates the integrated circuit on pin 1, while the coil is grounded via pin 2 to grounding point G3. Communication on the VR bus takes place on pin 4 with signal ground via pin 3 to grounding point G36.
The STC control module controls each valve with the message "Hydraulic valve X, unit ON/OFF" on the VR bus.