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E46iCCVM/ST039/3/21/00
Hydraulic System Operation
The pump in the hydraulic unit is energized by the CVM and supplies hydraulic fluid under
pressure to the solenoids mounted on the pump and solenoid valve block. The solenoids
are energized by the CVM and the pressure is supplied to the hydraulic cylinders, based on
the input signals from the angle hall sensors and hall switches. The hydraulic operation of
the solenoids and cylinders is as follows:
• The storage cover cylinders receive hydraulic pressure on the lowering side of the piston
ram when the hydraulic pump is energized. When the solenoid is energized, hydraulic pres-
sure is applied to the raising side of the ram. The cover is opened because the greater rais-
ing pressure overcomes the pressure on the small side of the ram. When the cover is low-
ered, the solenoid switches to drain and the lowering pressure closes the cover.
• The main pillar cylinders receive hydraulic pressure on both sides of the ram when the
pump is switched on. The main pillar solenoid is switched to drain to lower the top frame
into the storage compartment. The solenoid is switched to pressure to raise the top frame
out of the storage compartment. The greater pressure on the raise side of the piston will
overcome the lowering pressure to raise the frame.
• The raise tension bow solenoid is energized to apply pressure to the tension bow cylin-
ders and raise the tension bow. The tension bow lower solenoid is switched to drain.
• The lower tension bow solenoid is energized to supply pressure to the tension bow cylin-
ders to lower the tension bow. The tension bow raise solenoid is switched to drain.
• The drain solenoid is energized whenever the pump is switched on. It holds pressure in
the system when any of the cylinder solenoids are not energized. It also holds pressure in
the system if the top switch is released during operation.
The drain solenoid is switched when the hydraulic pump is switched off as the top reach-
es one of its end positions. This allows the pressure in the cylinders to be relieved and
drained back to the reservoir.
The drain solenoid switches off as the key is switched off. This will cause the pressure to
drain slowly in steps.