785G Off-Highway Truck Systems Caterpillar

Introduction

Note: Before adjusting the truck body up limit switch, the pad assemblies and the shims must be installed. Refer to Systems Operation/Testing and Adjusting, "Pad Assembly (Truck Body) - Install and Adjust" for the proper installation of the pad assemblies.

Illustration 1	g06193918
The output of the truck bed position sensor is a pulse width modulated (PWM) signal. The range of the output is 05 V to 4.5 V.

Rotary position sensor can be rotated 360 degrees. The PWM output for this sensor will only produce a continuous duty cycle over a range of 120 degrees. The duty cycle range is 5% to 95%. The output of the sensor begins at 5% when rotated past 90 degrees from center. In the counterclockwise direction the output of the sensor begins at 95% when rotated past 150 degrees from center.

Note: Before adjusting the rotary sensor, check that the sensor is mounted in the correct orientation.

Test Preparation

1. Raise the dump body and install the body retaining pins to secure the dump body in the UP position.
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   Illustration 2	g06193913
   Location of the position sensor for the truck bed (1) Rod adjustment locations (2) Rotary position sensor

   Note: Locate the truck bed position sensor. The rotary position sensor, used to determine the position of the truck bed, is on the left side of the machine, forward of the rear tire.

2. Rotate the sensor to align with the adjustment arm and secure.

Test Procedure

1. Inside the cab of the truck, turn the key switch to the "Key ON" position. (Do not start the engine.)

2. On the truck information display screen, press the payload button, on the left side of the screen.

3. When the "Calibrated Payload" appears, identify the "Payload Truck Icon". The icon in on the lower right side of the display.
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   Illustration 3	g06194115

4. Confirm that the icon is displaying the "Dumping Payload Truck Icon".

5. If the icon is not displayed check the position of the linkage and the position sensor to correct the problem.

6. Remove the body retaining pins and lower the dump body into the DOWN position.

7. To adjust the snub position of the dump body to approximately 200 to 300 mm (8 to 12 inch) between the front of the body pads and the frame rail, cycle the dump body and observe the SNUB position. If the dump body reaches the SNUB position too early, move the actuator arm of the sensor upward. If the dump body reaches the SNUB position too late, move the actuator arm of the sensor downward.

8. Repeat Step 7 until the desired SNUB position of the dump body is obtained.

9. Inside the cab of the truck, turn the key switch to the "Key ON" position. (Do not start the engine.)

10. On the truck information display screen, press the payload button, on the left side of the screen.

11. When the "Calibrated Payload" appears, identify the "Payload Truck Icon". The icon in on the lower right side of the display.
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    Illustration 4	g06194117

12. Confirm that the icon is displaying the "Stopped Empty Truck Icon".

Adjustment Procedure

If the icon is not displayed, check the position of the linkage and the position sensor and adjust the position.

Run the test procedure and adjust again, if necessary. Repeat the process beginning at Step 2.