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Personal injury can result from removing hoses or fittings in a system under pressure. Failure to relieve pressure can cause personal injury. Do not remove or disconnect hoses or fittings until all pressure in the hydraulic system has been relieved. |
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| 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. |
A resolver operates in a manner that is similar to a check valve. Resolvers are used to compare two pressures. The higher pressure causes the valve to move against the lower pressure. The valve seats and the low pressure oil is blocked. The high pressure oil flows through the opening that was created by the shifting of the valve.
There is one resolver per implement control valve. This joining of resolvers creates a resolver network. The network is designed to allow the highest signal pressure to be felt at the pressure and flow compensator valve of the hydraulic pump. For example, if more than one implement is being operated, the implement with the highest pressure will counteract the implements that are operating at lower pressures. The higher pressure causes the resolvers with the lower pressures to seat. This allows the highest pressure to be felt at the pressure and flow compensator valve. The compensator valve will then adjust the displacement of the pump in order to meet the system requirement.
Test
| Required Tools | |||
| Tool | Part Number | Part Description | Qty |
| A | 8T-0860 | Pressure Gauge | 1 |
| 6V-3989 | Test fitting | 1 | |
| 177-7861 | Hose | 1 | |
| 6V-4143 | Coupler | 2 | |
- Ensure that the machine is parked on a hard, smooth surface. Chock the wheels and engage the parking brake.
- Attach Tooling (A) to test fitting (1) for signal pressure.
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| Illustration 1 | g00742914 |
(1) Test fitting | |
- Start the engine. Lower the boom.
- Extend the boom and retract the boom several times in order to warm the hydraulic oil.
- Operate each implement several times in order to circulate the warm oil. Rotate the steering wheel from stop to stop several times.
- Stall the implements in the following order:
- One of the stabilizers (if equipped)
- Frame level (if equipped)
- Auxiliary
- Fork tilt
- Boom retract
- Boom lower
- Steering
Observe the gauge during the operation of the implements. Maximum signal pressure should be reached with each implement.
- implement pressure 22220 ± 344 kPa (3223 ± 50 psi)
- steering system pressure 17500 ± 500 kPa (2538 ± 73 psi)
- auxiliary pressure 12400 ± 500 kPa (1800 ± 73 psi)
Small leakage problems may be detected by using the pressure gauge.
- One of the stabilizers (if equipped)
Resolvers with Two or More Valve Sections
If two or more adjacent control valves fail to work properly, the problem may be in the resolver of an upstream implement control valve. If the resolver for the control valve does not function properly, signal oil from implements that are downstream may leak back through the bridge passage in the suspect valve to the tank. This leakage may be caused by a resolver that is not seating. When this occurs, the pump will not respond to the needs of the activated circuits.
A leakage in the resolver may be caused by a missing resolver or debris that prevents the resolver from properly seating. When multiple control valves malfunction, first operate the malfunctioning valve that is farthest from the pump. Operate the other control valves one at a time in the specified sequence. Operate the control valve that is farthest from the pump simultaneously.
When both of the implements that are being operated respond normally, the control valve with the bad resolver has been found. The farthest control valve is sending a signal and the control valve with the faulty resolver is also sending a signal. Because the control valve with the bad resolver has a leak, the signal from the farthest control valve cannot flow to the pump controller until the control valve with the faulty resolver is operated.