jcb 1CX, Service Manual

Page: 127 / 242

9 - 2
Pressure Reducing Solenoid Valve
(up to machine no. 751599)
This valve supplies hydraulic oil at reduced pressure to
operate the loader joystick and the automatic parking brake.
It is controlled by the seat position switch, the override
switch and the park brake switch.
It contains a reducing valve cartridge and a 3 position, 3 port
cartridge solenoid valve.
The relevant sections of the hydraulic and electrical circuits
are shown on the opposite page. Refer to the left hand
electrical schematic.
When first entering the machine, assuming the starter switch
is OFF, there is no hydraulic pressure as the auxiliary pump
is not running and the solenoid valve is in position X as there
is no electrical supply.
If the parking brake is ON (switch 17 in the position shown)
and the seat facing forward (seat switch 20 closed), starting
the engine energises the interlock relay 16 and solenoid 18,
moving the solenoid valve to position Y.
In this position the valve directs hydraulic power via the
loader joystick to the loader valve and other circuits, but the
brake pressure is still dumped to tank.
Operation of the parking brake switch 17 de-energises
solenoid 18 and energises solenoid 19. This causes the
solenoid valve to move to position Z, directing hydraulic
power via the loader joystick as before, but also pressurising
the brake circuit (brakes OFF).
If the seat is rotated to face the rear of the machine, seat
switch 20 opens, de-energising relay 16. Both solenoids 18
and 19 de-energise, and the solenoid valve returns to
position X. In this condition, pressure from the auxiliary
pump is dumped to tank (brakes ON and no hydraulic
pressure available at the loader joystick).
When the override switch 21 is closed, the seat switch 20 is
by-passed allowing the loader to be used with the seat
facing rearwards.
Key to L. H. Electrical Schematic
(up to machine no. 751599)
16 Interlock Relay
17 Parking Brake Switch
18 Operational Solenoid
19 Parking Brake Solenoid
20 Seat Switch
21 Override Switch
Pressure Reducing Solenoid Valve
(from machine no. 751600)
This valve supplies hydraulic oil at reduced pressure to
operate the loader joystick and the automatic parking brake.
It is controlled by the seat position switch, the override
switch and the park brake switch.
It contains a reducing valve cartridge and a 3 position, 3 port
cartridge solenoid valve.
The relevant sections of the hydraulic and electrical circuits
are shown on the opposite page. Refer to the right hand
electrical schematic.
When first entering the machine, assuming the starter switch
is OFF, there is no hydraulic pressure as the auxiliary pump
is not running and the solenoid valve is in position X as there
is no electrical supply.
If the parking brake is ON (switch 7 in the position shown)
and the seat facing forward (seat switch 14 closed), starting
the engine energises the isolation relay 12 and solenoid 9,
moving the solenoid valve to position Y.
In this position the valve directs hydraulic power via the
loader joystick to the loader valve and other circuits, but the
brake pressure is still dumped to tank.
Operation of the parking brake switch 7 de-energises
solenoid 9 and energises solenoid 10. This causes the
solenoid valve to move to position Z, directing hydraulic
power via the loader joystick as before, but also pressurising
the brake circuit (brakes OFF).
If the seat is rotated to face the rear of the machine, seat
switch 14 opens, de-energising relay 12. Both solenoids 9
and 10 de-energise, and the solenoid valve returns to
position X. In this condition, pressure from the auxiliary
pump is dumped to tank (brakes ON and no hydraulic
pressure available at the loader joystick).
When the override switch 11 is closed, the seat switch 14 is
by-passed allowing the loader to be used with the seat
facing rearwards.
Key to R. H. Electrical Schematic
(from machine no. 751600)
7 Parking Brake switch
8 Parking Brake Solenoid
9 Operation Solenoid
10 Parking Brake Solenoid
11 Override Switch
12 Isolation Relay
14 Seat Switch
Section E Hydraulics
9803/8550
Section E
9 - 2
Issue 4
Descriptions
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