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| Illustration 1 | g00927062 |
(1) Steering cylinders (2) Steering metering unit (3) Hydraulic tank and filter (4) Implement and steering pump (5) Check valve (6) Check valve (7) Combination valve (8) Relief valve (9) Check valve (10) Pump (11) Electric Drive | |
System Operation
The secondary steering system provides hydraulic oil to the primary steering system in the event of a primary system failure.
Hydraulic oil is supplied from the hydraulic tank (3) to pump (10). Pump (10) pumps hydraulic oil to the combination valve (7). Hydraulic oil flows through combination valve (7) to the steering metering unit (2). When the operator turns the steering wheel, steering metering unit (2) supplies regulated amounts of hydraulic oil to steering cylinders (1) .
Three check valves are installed in the steering system in order to prevent a loss of hydraulic oil backward through the system.
Check valve (6) is installed in combination valve (7). Check valve (6) prevents the hydraulic oil from pump (10) from entering the primary supply passage in the combination valve.
Check valve (5) is installed in the signal line from combination valve (7) to steering metering unit (2). Check valve (5) prevents the loss of signal oil from steering metering unit (2) backward into the primary hydraulic system through combination valve (7) .
Check valve (9) is installed in the supply line to combination valve (7). When pump (10) is not running, check valve (9) prevents the loss of hydraulic oil from combination valve (7) backward through the secondary steering system.
At 17225 kPa (2498 psi), relief valve (8) opens. Relief valve (8) directs the hydraulic oil to hydraulic tank (3) .
Automatic Activation of the Secondary Steering System
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The machine's batteries must have a normal charge and the secondary steering electrical system must be okay. A low charge condition, or any defect in the battery, battery cells, or electrical circuit can cause loss of secondary steering and could result in personal injury and/or damage to the machine. |
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| NOTICE |
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The secondary steering motor may remain on for a maximum of two minutes. This time period should be long enough to safely steer the machine to a stop. After the machine has stopped, turn the engine start switch to the OFF position in order to turn off the secondary steering system. Prolonged use of the secondary steering system will cause the secondary steering motor to overheat. Overheating of the secondary steering motor may cause damage to the components of the secondary steering motor. |
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| Illustration 2 | g00922795 |
(10) Pump (11) Electric drive | |
While the secondary steering system is in the automatic mode, the secondary steering system provides backup hydraulic oil flow under two conditions.
- The engine fails.
- While the engine is running, the hydraulic system pressure drops below 700 ± 103 kPa (100 ± 15 psi).
While the machine is running, the secondary steering system will be in the automatic mode. In the automatic mode, the spring loaded secondary steering test switch will rest in the NORMAL position.
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| Illustration 3 | g00922794 |
(12) Pressure switch | |
If the primary steering system pressure falls below 700 ± 103 kPa (100 ± 15 psi), pressure switch (12) will open.
The opening of pressure switch (12) sends a signal to the secondary steering control. The secondary steering control turns on the following components:
- Action light
- Magnetic switch
- Electric drive
- Warning light
Electric drive (11) drives pump (10). Pump (10) charges the steering system with hydraulic oil.
Manual Activation of the Secondary Steering System
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| Illustration 4 | g00920822 |
(13) Warning light | |
Manual activation of the secondary steering system may be used to turn the steering wheel while the secondary steering system is being tested. If the machine is being towed, manual activation may also be used in order to perform steering adjustments.
The manual activation of the secondary steering system will operate regardless of the key switch position. As follows, activate the manual mode of the secondary steering system:
Hold the secondary steering test switch in the TEST position. The secondary steering test switch will energize the magnetic switch. The magnetic switch will energize electric drive (11). The magnetic switch will energize the warning light (13) .
Electric drive (11) drives pump (10). Pump (10) charges the steering system with hydraulic oil. A status light in the secondary steering test switch will be illuminated whenever pump (10) is energized.