| NOTICE |
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Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates. |
Test the Stem for Binding
Prepare the machine for maintenance. Relieve the system pressure.
Note: Do not warm the oil.
Refer to Testing and Adjusting, "General Information".
- Remove pilot control actuator (1) and pilot control actuator (3). Refer to Disassembly and Assembly, RENR3402, "Hoist Control Valve - Disassemble".
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| Illustration 1 | g00722881 |
The ejector control valve is located to the right of the transmission. (1) Pilot control actuator (2) Body of the ejector control valve (3) Pilot control actuator | |
- Check if the stem will slide in the body of the ejector control valve. Remove the stem and check for excessive wear or scoring. Also check for contamination in the ejector control valve.
Note: Do not grind the stem in any way. Do not place another stem in the body of the ejector control valve. The stem is matched to the valve body.
- If there is any contamination in the ejector control valve, disassemble the ejector control valve and remove the contamination. Refer to Disassembly and Assembly, RENR3402, "Hoist Control Valve - Disassemble".
- If the ejector control valve has been removed, install the ejector control valve.
Test the Stem for Centering
Prepare the machine for maintenance. Warm the oil. Relieve the system pressure. Refer to Testing and Adjusting, "General Information".
The stem is centered to the HOLD by equal pilot pressure and by equal current within the pilot control actuators. This test will establish whether the pilot pressures and the currents are equal at either side of the stem.
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| Illustration 2 | g00722881 |
The ejector control valve is located to the right of the transmission. (1) Pilot control actuator (2) Body of the ejector control valve (3) Pilot control actuator | |
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| Illustration 3 | g00625598 |
Typical pilot control actuator (4) Typical proportional solenoid (5) Typical pilot control actuator (6) Control pressure port (7) Typical tank port (8) Typical wiring harness | |
- Ensure that the oil for the hydraulic system is at operating temperature. Park the machine on a level surface. Apply the parking brake. Stop the engine and install the steering frame locks. Refer to Operation and Maintenance Manual, SEBU7379, "Install Steering Frame Locks".
- Connect a 7000 kPa (1000 psi) or greater gauge to the control pressure port (6) of each actuator. The hose for the pressure gauge should run into the cab of the truck.
- Start the engine and run the engine at low idle.
- Read the control pressure at each pilot control actuator. The control pressures should match.
- If the control pressures do not match, stop the engine and disconnect the wiring harnesses (8) on each actuator. Start the engine and run the engine at low idle. Check if the control pressures match. If the control pressures match, check the supply voltage of each actuator. The voltages should match. If the voltages do not match, check for diagnostic codes on the EMS display on the right dashboard.
- If the control pressures do not match, stop the engine and make sure that the hydraulic pressure is zero. Remove both pilot control actuators and check for broken springs. Replace any broken springs. If there are no broken springs, there may be a leak in the pilot control actuator. Repair the pilot control actuator.
- Install any parts that were removed.
- Remove all test equipment from the machine.
Test the Actuator Solenoids
Prepare the machine for maintenance. Warm the oil. Relieve the system pressure. Refer to Testing and Adjusting, "General Information".
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| Illustration 4 | g00722881 |
The ejector control valve is located to the right of the transmission. (1) Pilot control actuator (2) Body of the ejector control valve (3) Pilot control actuator | |
- Disconnect the wiring harness to the suspected proportional solenoid. Check the resistance between the two pins on the harness for the proportional solenoid. The resistance should be 6.5 ± 0.4 Ohms.
- If the resistance is not 6.5 ± 0.4 Ohms, connect the proportional solenoid to the wiring harness. Turn the service switch to the SERVICE position. Start the engine and check for a change in current in the wire as an assistant presses the eject button. Also check for a change in current as an assistant presses the retract button.
- If an appropriate change in current is not detected, the solenoid is malfunctioning. Replace the proportional solenoid which is malfunctioning. Refer to Disassembly and Assembly, RENR3402, "Hoist Control Valve - Disassemble".
- Install any parts that were removed.
- Remove all test equipment from the machine.