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| Illustration 1 | g06119898 |
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Hydraulic Schematic for Steering Systems that use Hand Metering Units (1) Steering pump (2) Hand metering unit (HMU) (3) Left steering cylinder (4) Right steering cylinder (5) Breather (6) Hydraulic oil tank (7) Load sense signal line (8) Secondary steering pump/motor. (optional attachment) (9) Secondary steering valve. (optional attachment) (10) Check valve (11) Check valve (12) Secondary steering pressure switch (15) Relief valve for secondary steering (16) Primary steering pressure sensor (AA) Pressure tap for checking steering pump pressure (BB) Pressure tap for checking signal pressure | |
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| Illustration 2 | g06111128 |
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Component Locations for the Secondary Steering System Left Side View (3) Left steering cylinder. (8) Secondary steering pump/motor. (optional attachment). (9) Secondary steering valve.(optional attachment). | |
Note: The secondary steering system is an attachment for these machines. The secondary steering system provides oil flow to the steering controls when the primary steering system pressure is too low. The secondary steering system should not be used in normal operation.
The secondary steering system consists of the following components: secondary steering pump and electric motor (16) and secondary steering diverter valve (9). These components continue to provide oil flow to the primary steering controls in the event of a loss of primary steering oil flow.
Secondary steering valve (9), and secondary steering pump and electric motor (8) are on the lower left frame.
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| Illustration 3 | g03437216 |
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Location of steering indicators on the front dashboard. | |
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| Illustration 4 | g03437217 |
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(13) Secondary steering indicator. | |
Machines with the secondary steering system installed, have a check valve installed in the steering diverter valve (9). During normal machine operation, check valve (10) is off the seat, while check valve (11) is seated. Check valve (11) prevents primary pressure oil from flowing back to secondary steering pump (15).
If the primary steering pump (8) or engine fails, the primary steering pressure switch (16) will open detecting the low pressure. The transmission ECM will then activate the secondary steering pump (8) and send a signal to the monitoring system. The monitoring system then causes a Warning Category 3 alarm to occur.
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The alarm system indicates that the primary steering system has failed. Continuing to operate the machine could result in additional damage to the steering system components. Use the secondary steering system to steer the machine to a safe stop immediately. When the machine comes to a complete stop, turn the start switch key to the OFF position and remove the key. Investigate the cause of the problem before resuming operation. Do NOT use the secondary steering system as a limp-home mode procedure. Do NOT use the secondary steering system for steering the machine when the machine is being towed. |
A Warning Category 3 alerts the operator that engine shutdown should occur as soon as possible. This action helps prevent injury to the operator and potential damage to the machine.
A Warning Category 3 causes both the master action light and secondary steering indicator (13) to turn on. A Warning Category 3 also causes the action alarm to sound. Do not operate the machine until the cause has been corrected.
Secondary steering pump and electric motor (8) draw oil from hydraulic oil tank (6). The oil then flows to secondary steering check valve group (9). This causes check valve (11) to unseat. The oil pressure then causes check valve (10) to seat. This process prevents pressure oil from flowing back to HMU (1). The pressure oil then flows to steering metering pump (2).
The secondary steering system is tested each time the engine is started. After the engine is running, a 3 second test is performed. During the test, the secondary steering indicator (13) turns on. The transmission ECM detects if the secondary steering system pressure status through the secondary steering pressure switch (12). If the secondary steering pump provides the desired pressure, the switch closes and the test is successful. If the pressure does not reach the desired level, then the test fails and an event is logged. The machine should not be used until the reason for failure is determined and repaired.
Note: The machine can be articulated during the three second test.
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| Illustration 5 | g03438714 |
| (14) Secondary steering test switch | |
The secondary steering system can be manually tested. Test switch (14) for the secondary steering system is on the lower right console. Test switch (14) is a momentary on, normally open switch.
Push test switch (14) to determine if secondary steering pump and electric motor (8), and secondary steering indicator (13) are operational. When test switch (14) is pushed, secondary steering pump and electric motor (8) to run. This action causes secondary steering indicator (13) to turn on. This action also causes the action alarm to sound.
Relief valve (15) is for the secondary steering pump. Relief valve (15) limits the amount of oil pressure in the secondary steering circuit.