Operation and maintenance manual

Section 250-0065
1
SM 2159 7-02
DESCRIPTION
Numbers in parentheses refer to Fig. 1. The two speed
control valve can be identified as item 5 in Section
210-0005, COOLING SYSTEM SCHEMATIC.
Mounted on the disc brake oil cooler casing on the
right hand fender, the two speed control valve
regulates the fan speed of the disc brake oil cooler.
The two speed control valve houses two valves: two
way solenoid operated cartridge (1) and flow regulator
cartridge (2).
The two speed control valve is supplied by a dedicated
brake cooling section (rear section) of the triple gear
pump, via pressure relief valve. The solenoid cartridge
(1) controls flow to the hydraulically driven disc brake
oil cooler fan motor. The flow regulator cartridge (2)
controls the flow rate through the solenoid to a preset
supply of 10 litres/min.
OPERATION
Numbers in parentheses refer to Fig. 1.
The two speed control valve has 2 ports, an inlet port
and an outlet port. The inlet port is connected to the
outlet port via the flow regulator cartridge (2) and the
two way solenoid cartridge valve (1).
Refer to Fig. 2. The two speed control valve forms part
of the disc brake oil cooler fan speed control system.
With the solenoid cartridge (1) de-energised, the
majority of the available hydraulic oil will be allowed to
flow through the two speed control valve at a rate of 10
litres/min. The remainder of the available hydraulic oil
will be forced to circulate the disc brake oil cooler fan
motor, thus rotating the fan.
Refer to Fig. 3. The normally open temperature switch
on the front axle manifold valve closes when disc
brake cooling oil temperature reaches 50°C (122°F),
energising the solenoid cartridge (1). When the
solenoid cartridge (1) is energised, hydraulic oil is
prevented from flowing through the valve and is forced
through the disc brake oil cooler fan motor, thus
increasing the fan speed.
FUNCTIONAL CHECK
Numbers in parentheses refer to Fig. 1.
To check proper operational function of the two speed
control valve, refer to following procedure.
BRAKING SYSTEM - Two Speed Control Valve
SM - 2752
1 - Solenoid Cartridge
2 - Flow Regulator Cartridge
3 - Valve Body
4- Washer
5 - Lockwasher
6- Bolt
Fig. 1 - Two Speed Control Valve
SM - 2753
Fig. 2 - Two Speed Control Valve -
Solenoid De-energised
SM - 2754
Fig. 3 - Two Speed Control Valve -
Solenoid Energised
FROM TRIPLE
GEAR PUMP
TO DISC BRAKE
OIL COOLER
FROM DISC BRAKE
OIL COOLER
TO MOTOR/
TRIPLE PUMP
FROM TRIPLE
GEAR PUMP
TO DISC BRAKE
OIL COOLER
FROM DISC BRAKE
OIL COOLER
TO MOTOR/
TRIPLE PUMP
1
6
4
5
2
3