770G and 772G Off-Highway Truck (OEM) Hydraulic and Braking System770G and 772G Off-Highway Truck (OEM) Hydraulic and Braking System: Proportioning Solenoid (Hoist) - Test

Table 1

Required Tools
Part Number	Description	Required Amount
146-4080	Digital Multimeter Group	2
132-7842	Test Harness	2

Hoist control valve (1) Hoist proportioning solenoid for SNUB, FLOAT, and LOWER(2) Hoist proportioning solenoid for RAISE

1. Use Caterpillar Electronic Technician (ET) in order to determine if there are any active diagnostics in the Chassis ECM for any of the following parameters:
   
   
   • Hoist raise solenoid current
   • Hoist lower solenoid current
   • Hoist lever position sensor
   • Hoist lever duty cycle

2. Install multimeters.
   
   
   1. Install a multimeter in series with hoist proportioning solenoid (1) .
   
   
   2. Install a multimeter in series with hoist proportioning solenoid (2) .

Typical



3. Monitor status parameters with the use of ET.
   
   
   1. Use Caterpillar Electronic Technician (ET) in order to monitor the following four status parameters in the Chassis Electronic Control Module (ECM):
      
      
      • Hoist raise solenoid current
      • Hoist lower solenoid current
      • Hoist lever position sensor
      • Hoist lever duty cycle
      Note: The Caterpillar Monitoring System can also be used to monitor the hoist raise solenoid current and the hoist lower solenoid current.

Note: The tests can be ran with greater safety with the engine in the OFF position and a disabled safety Hold feature.


4. Disable the safety HOLD feature with the following procedure:
   
   
   1. Raise the body, install the safety pins, and STOP the engine.
   
   
   2. Turn the key start switch to the ON position.
   
   
   3. Move the hoist lever to the RAISE position for 15 seconds. Move the hoist lever to the HOLD position. Now when the hoist lever is moved to the various positions, the hoist output will change.

5. Take readings for the HOLD position.
   
   
   1. Move the hoist control lever to the HOLD position.
   
   
   2. Record the readings for both status parameters that are displayed in ET.
   
   
   3. Record the readings that are displayed on both multimeters.
   
   
   4. Record the readings that are displayed for the hoist lever duty cycle.

6. Take readings for the RAISE position.
   
   
   1. Move the hoist control lever to the RAISE position.
   
   
   2. Record the readings for both status parameters that are displayed in ET.
   
   
   3. Record the readings that are displayed on both multimeters.
   
   
   4. Record the readings that are displayed for the hoist lever duty cycle.

7. Take readings for the LOWER position.
   
   
   1. Move the hoist control lever to the LOWER position.
   
   
   2. Record the readings for both status parameters that are displayed in ET.
   
   
   3. Record the readings that are displayed on both multimeters.

8. Record the readings that are displayed for the hoist lever duty cycle.

9. Take readings for the FLOAT position.
   
   
   1. Move the hoist control lever to the FLOAT position.
   
   
   2. Record the readings for both status parameters that are displayed in ET.
   
   
   3. Record the readings that are displayed on both multimeters.

10. Record the readings that are displayed for the hoist lever duty cycle.

11. Disconnect the tools that were used in the above procedure.
    
    
    1. Disconnect both multimeters.
    
    
    2. Disconnect Caterpillar Electronic Technician (ET)

12. Evaluate the readings that were taken in the above steps. Compare the recorded values with the values in Table 2.
    
    
    1. Calculate target values for table 2. Identify the formulas that are shown in the footnotes of table 2. Use these formulas and the appropriate readings from ET to obtain the calculated target values for table 2.
    
    
    2. For each position of the hoist control lever, compare the recorded readings from the multimeters to the values for table 2.

Table 2

Hoist Control Lever	Duty Cycle	Current to Solenoid (1)	Current to Solenoid (2)
HOLD	55 to 71%	0.0 to 0.1 amp	0.0 to 0.1 amp
RAISE	80 to 96%	0.0 to 0.1 amp	Calculated target value (1) ± 0.2 amp
LOWER	1 to 18%	Calculated target value (2) ± 0.2 amp	0.0 to 0.1 amp
FLOAT	24 to 48%	Calculated target value (2) ± 0.2 amp	0.0 to 0.1 amp

( 1 )	The formula for calculating this target value is: (Hoist Raise Solenoid Current ÷100)×(2.0) amp. The Hoist Raise Solenoid Current is expressed as a percentage. This value is obtained by using Electronic Technician.
( 2 )	The formula for calculating this target value is: (Hoist Lower Solenoid Current ÷100)×(2.0) amp. The Hoist Lower Solenoid Current is expressed as a percentage. This value is obtained by using Electronic Technician.

Problem: The values do not match the table.

Probable Cause

• The hoist control position sensor is not sending the correct signal to the Chassis Electronic Control Module (Power Train ECM). Use Caterpillar Electronic Technician (ET) to view the input signal to the Power Train ECM.
• The hoist proportioning solenoid or the wiring from the Chassis ECM has failed.

Note: The Caterpillar Monitoring System can also be used to view the input signal to the Power train ECM.

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