In order to make a sharp left turn, the operator pulls the steering control lever fully backward. The steering clutch is released and the brake is engaged. The control valve modulates down the clutch pressure. The pressure falls below the calibrated value for low pressure in the steering clutch. Therefore, the clutch is released. Also, the control valve reduces the brake pressure until a residual pressure is reached. Then, the brakes are fully applied. This is the normal operation. When there is a problem with this process, the machine will not make a sharp left turn.
The possible causes of this problem are listed below:
- The left steering lever does not have the correct operating range.
- The control valve does not modulate the clutch pressure properly.
- The control valve does not modulate the brake pressure properly.
- The brake module is functioning incorrectly.
Test Step 1. CHECK THE OPERATING RANGE OF THE LEFT STEERING LEVER.
- Turn the key start switch to the ON position.
- Access the component data display mode. View the value of the position sensor (left steering). This is component 676. See Testing and Adjusting, "Calibration" for more information.
- Record the value for the left steering lever when the lever is released.
- Pull the left steering lever fully backward and record the value for the sensor.
Expected Result:
The duty cycle range that is shown on the display changes by at least 61%.
Results:
- OK - The duty cycle range that is shown on the display changes by at least 61%. Proceed to Test Step 2.
- NOT OK - The duty cycle range that is shown on the display does not change by at least 61%.
Repair: Adjust the stop for the steering lever until the lever has the correct range. If the correct range cannot be obtained, replace the position sensor.
STOP
Test Step 2. CHECK THE MODULATION OF THE CLUTCH AND BRAKE PRESSURE.
Enter the calibration mode on the monitoring system. Perform the calibrations for the steering and braking. These calibrations are submode 2 through submode 9. Ensure that the calibrations are adjusted to the correct pressures.
Expected Result:
After the calibrations, the machine turns properly.
Results:
- YES - After the calibrations, the machine turns properly.
STOP
- NO - After the calibrations, the machine does not turn properly.
Repair: There is a problem with the control valve for the steering and brakes. Repair the control valve. Also, check the brake module for worn material or damaged material. See the Testing and Adjusting manual for the steering system of the machine that is being serviced.
STOP