950G Series II Wheel Loader and 962G Series II Wheel Loader Electrohydraulic System Caterpillar

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Dry nitrogen is the only gas approved for use in the accumulators. The charging of oxygen gas in an accumulator will cause an explosion. An explosion can be eliminated by using nitrogen gas cylinders with standard CGA (Compressed Gas Association, Inc.) No. 580 connectors. When nitrogen gas is ordered, make sure to order the cylinders with CGA No. 580 connectors. Do not rely on color codes or other methods of identification to tell the difference between nitrogen and oxygen cylinders. In any application, never use an adapter to connect your nitrogen charging group to a valve outlet used on both nitrogen, oxygen, or other gas cylinders. BE SURE YOU USE DRY NITROGEN (99.8% purity).

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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

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Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.

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Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine. To prevent personal injury or death, perform the following: Park the machine on a smooth, level surface. Lower the work tool to the ground and engage the parking brake. Stop the engine and remove the key. Block the wheels and install the steering frame lock.

Shutdown Procedure

1. Start the engine.

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Illustration 1	g00800462
Cab Controls (Right Side) (1) Ride control switch

2. Move ride control switch (1) to the ON position.

3. Lower all attachments to the ground.

4. Move the lift control lever to the FLOAT position. This will relieve all of the hydraulic pressure in the accumulator.

5. Turn the engine start switch key to the OFF position.

6. Disconnect the hydraulic lines for servicing, as needed.

Discharging the Accumulator

If the accumulator must be replaced, first perform the "Shutdown Procedure". Then perform the following steps.

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Illustration 2	g00833449
Location of the Ride Control Accumulator in the Loader Frame The ride control accumulator is located inside the front frame on the right side of the machine.

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Illustration 3	g00297440
Ride Control Accumulator (2) Nitrogen charging valve.

1. Remove the protective cap on nitrogen charging valve (2) .

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Illustration 4	g00282185
Nitrogen Charging Group (3) Nipple. (4) Coupling assembly. (5) Pressure gauge. (6) Hose assembly. (7) Coupling assembly. (8) Nipple. (9) Valve. (10) Pressure gauge. (11) Regulator assembly. (12) Pressure regulating screw. (13) Chuck for the nitrogen cylinder valve. (14) Valve handle. (15) Chuck. (16) Hose assembly. (17) Tee.

2. Identify the correct nitrogen charging chuck.

   Note: For a nitrogen charging valve with a .305 inch - 32 THD, use a 1S-8938 Nitrogen Charging Chuck . For a nitrogen charging valve with a .482 inch - 26 THD, use a 7S-5106 Nitrogen Charging Chuck .

Note: Do not attach hose assembly (16) to tee (17) when you are discharging the accumulator.

3. Attach hose assembly (16) to nitrogen charging chuck (15) .

4. Turn valve handle (14) on chuck (15) all the way in the counterclockwise direction. This will ensure that nitrogen charging valve (2) will not open when chuck (15) is attached to nitrogen charging valve (2) .

5. Attach chuck (15) and hose assembly (16) to nitrogen charging valve (2) .

6. Place the open end of hose assembly (16) away from the work area and away from other personnel.

7. Turn valve handle (14) on chuck (15) all the way in the clockwise direction in order to open nitrogen charging valve (2) . This will release all of the compressed gas from the ride control accumulator through hose assembly (16) . Now, the ride control accumulator can be removed from the machine.

Nitrogen Charging Procedure

1. Move the machine to level ground.

2. Move the transmission direction control lever to the NEUTRAL position. Move the transmission neutralizer lockout switch to the OFF position.

3. Engage the parking brake.

4. Start the engine. Keep the engine running during the following steps. This will ensure that a flow of pilot oil is available to shift the diverter valve spool when the ride control switch is turned to the ON position.

5. Move the lift control lever to the FLOAT position. Turn the ride control switch to the ON position.

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Illustration 5	g00297440
Ride Control Accumulator (2) Nitrogen charging valve.

6. The ride control accumulator is located near the articulation hitch in the loader frame on the right side of the machine. Remove the protective cap on nitrogen charging valve (2) .

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Illustration 6	g00282185
Nitrogen Charging Group (3) Nipple. (4) Coupling assembly. (5) Pressure gauge. (6) Hose assembly. (7) Coupling assembly. (8) Nipple. (9) Valve. (10) Pressure gauge. (11) Regulator assembly. (12) Pressure regulating screw. (13) Chuck for the nitrogen cylinder valve. (14) Valve handle. (15) Chuck. (16) Hose assembly. (17) Tee.

7. Turn tee handle (14) on chuck (15) all the way in the counterclockwise direction. Attach appropriate chuck (15) to nitrogen charging valve (2) .

   Note: For a nitrogen charging valve with a .305 inch - 32 THD, use a 1S-8938 Nitrogen Charging Chuck . For a nitrogen charging valve with a .482 inch - 26 THD, use a 7S-5106 Nitrogen Charging Chuck .

8. Attach hose assembly (16) between chuck (15) and tee (17) . Install needle valve (9) on one of the connecting points of the tee. Install 8T-0858 Pressure Gauge (10) in the remaining open port on the tee. The pressure gauge is rated at 0 to 16000 kPa (0 to 2300 psi).

9. Install coupling assembly (7) in the end of hose assembly (6) .

10. Install nipple (8) on needle valve (9) . Place the open end of hose assembly (6) away from the work area and away from other personnel.

11. Open needle valve (9) and turn tee handle (14) on chuck (15) all the way in the clockwise direction.

12. Raise the work tool to the maximum height in order to relieve any additional nitrogen from the ride control accumulator.

13. Lower the work tool to the ground. Move the lift control lever to the FLOAT position.

14. Close needle valve (9) .

15. Install nipple (3) in the end of hose assembly (6) .

16. Attach the open end of hose assembly (6) to regulator assembly (11) . Install an 8T-0859 Pressure Gauge in the port that is directly above the regulator. This pressure gauge is rated at 0 to 25000 kPa (0 to 3600 psi).

17. Install an 8T-0856 Pressure Gauge in the remaining port next to regulator assembly (11) . This pressure gauge is rated at 0 to 6000 kPa (0 to 870 psi).

18. Install regulator assembly (11) on the nitrogen tank valve. Adjust screw (12) on regulator (11) in order to set the pressure on the 8T-0856 Pressure Gauge to the appropriate charge pressure.

    Note: To ensure that the accumulator nitrogen charge is correct, the accumulator piston must be at the bottom of the accumulator cylinder. Nitrogen pressure varies with the temperature. To obtain the most accurate nitrogen charge, the temperature of the accumulator should equal the outside air temperature. However, the temperature of the accumulator could be higher than the outside air temperature in some cases. If this is the case, the temperature of the accumulator should be used instead of the outside air temperature.

    Note: The pressures in Table for the 950G Series II Wheel Loader, the pressures in Table for the 962G Series II Wheel Loader, and the pressures in Table for the IT62G Series II Integrated Toolcarrier are recommended for machines with typical work tools. For machines with heavy buckets or work tools, the nitrogen pressure may need to be increased in order to keep the accumulator piston from striking an internal stop during normal roading while the ride control system is activated. However, raising the nitrogen pressure will result in a stiffer ride.

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    Table 2

    950G Series II Accumulator Precharge Pressure/Temperature Relationship for a Typical Ride Control Accumulator with a Precharge of 3270 kPa (475 psi)
    Temperature	Pressure (1)
    -7°C (20°F)	2994 kPa (435 psi)
    -1°C (30°F)	3049 kPa (443 psi)
    4°C (40°F)	3105 kPa (451 psi)
    10°C (50°F)	3160 kPa (459 psi)
    16°C (60°F)	3215 kPa (467 psi)
    21°C (70°F)	3270 kPa (475 psi)
    27°C (80°F)	3325 kPa (483 psi)
    32°C (90°F)	3380 kPa (491 psi)
    38°C (100°F)	3435 kPa (499 psi)
    43°C (110°F)	2491 kPa (507 psi)
    49°C (120°F)	2546 kPa (515 psi)

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    ( 1 )

    Nominal allowable tolerance equals ± 35 kPa (± 5 psi).

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    Table 3

    962G Series II Accumulator Precharge Pressure/Temperature Relationship for a Typical Ride Control Accumulator with a Precharge of 3270 kPa (475 psi)
    Temperature	Pressure (1)
    -7°C (20°F)	2994 kPa (435 psi)
    -1°C (30°F)	3049 kPa (443 psi)
    4°C (40°F)	3105 kPa (451 psi)
    10°C (50°F)	3160 kPa (459 psi)
    16°C (60°F)	3215 kPa (467 psi)
    21°C (70°F)	3270 kPa (475 psi)
    27°C (80°F)	3325 kPa (483 psi)
    32°C (90°F)	3380 kPa (491 psi)
    38°C (100°F)	3435 kPa (499 psi)
    43°C (110°F)	2491 kPa (507 psi)
    49°C (120°F)	2546 kPa (515 psi)

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    ( 1 )

    Nominal allowable tolerance equals ± 35 kPa (± 5 psi).

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    Table 4

    IT62G Series II Accumulator Precharge Pressure/Temperature Relationship for a Typical Ride Control Accumulator with a Precharge of 2070 kPa (300 psi)
    Temperature	Pressure (1)
    -4 °C (25 °F)	1792 kPa (260 psi)
    2 °C (35 °F)	1847 kPa (268 psi)
    7 °C (45 °F)	1902 kPa (276 psi)
    13 °C (55 °F)	1958 kPa (284 psi)
    18 °C (65 °F)	2013 kPa (292 psi)
    24 °C (75 °F)	2070 kPa (300 psi)
    30 °C (85 °F)	2123 kPa (308 psi)
    35 °C (95 °F)	2178 kPa (316 psi)
    41 °C (105 °F)	2233 kPa (324 psi)
    46 °C (115 °F)	2289 kPa (332 psi)
    52 °C (125 °F)	2344 kPa (340 psi)

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    ( 1 )

    Nominal allowable tolerance equals ± 35 kPa (± 5 psi).

19. Open needle valve (9) . The nitrogen pressure should show on the 8T-0858 Pressure Gauge within 20 seconds.

    Note: If the nitrogen pressure shows on the pressure gauge in less than 10 seconds, close screw (12) on regulator assembly (11) and needle valve (9) . Disconnect hose assembly (6) from needle valve (9) . Repeat Step through Step .

20. Turn tee handle (14) on chuck (15) all the way in the counterclockwise direction. Close regulator (11) and needle valve (9) . Slowly disconnect hose (6) from needle valve (9) . Open needle valve (9) . Remove chuck (15) from nitrogen charging valve (2) on the ride control accumulator.

21. Install the protective cap on the nitrogen charging valve (2) .

Testing the Ride Control Diverter Valve

The following procedure is used to determine whether the diverter valve is operating correctly. Perform this test after the ride control accumulator is charged.

Illustration 7	g00800462
Cab Controls (Right Side) (1) Ride Control Switch

1. Start the machine.

2. Move ride control switch (1) to the OFF position.

3. Place the bucket in the full DUMP position. Lift the front wheels off the ground by moving the lift control lever to the LOWER position.

4. When the front wheels are off the ground, place the lift control lever in the HOLD position. Toggle the ride control switch (1) to the ON position. In approximately 3 to 5 seconds, the ride control will activate and the front wheels should lower to the ground. The accumulator precharge pressure should be 2760 ± 35 kPa (400 ± 5 psi) at 21 °C (70 °F) for the 950G Series II Wheel Loader. The accumulator precharge pressure should be 3103 ± 35 kPa (450 ± 5 psi) at 21 °C (70 °F) for the 962G Series II Wheel Loader. The accumulator precharge pressure should be 2070 ± 35 kPa (300 ± 5 psi) at 24 °C (75 °F) for the IT62G Series II Wheel Loader.

   If the wheels do not lower to the ground, the diverter spool has not shifted to the ON position. The following conditions are probable causes:

   • The ride control switch is faulty.

   • The solenoid coil on the diverter valve is faulty.

   • The cartridge valve in the diverter valve is faulty.

   • The diverter valve spool sticks.

   • The pilot oil passage to the ride control diverter valve is blocked.

Road Test

Note: The pressures in Table and in Table are recommended for machines with typical work tools. For machines with heavy buckets or work tools, the nitrogen pressure may need to be increased in order to keep the accumulator piston from striking an internal stop during normal roading while the ride control system is activated. However, raising the nitrogen pressure will result in a stiffer ride.

1. Put a typical load in the work tool.

2. Position the ride control switch in the AUTO position.

3. Operate the machine to a speed of at least 10 km/h (6 mph). The ride control system should start about five seconds after the machine has reached 10 km/h (6 mph).

   If the machine bounces too much or the accumulator piston is striking the stop, the nitrogen precharge pressure must be increased.

   Note: The ride control accumulators are rated up to 20670 kPa (3000 psi). Only add enough nitrogen in order to achieve a suitable ride for the machine's typical payload.

4. Increase the nitrogen precharge pressure by 345 kPa (50 psi) and perform the road test again.