PLUG 0966448 - Caterpillar

Illustration 1 g01435858
Electrohydraulic Pilot Manifold (Blade Lower)
(1) Passage to Blade Lift Control Valve (Blade Lower)
(2) Passage to Ripper Tip Control Valve (Tip Out)
(3) Passage to Ripper Lift Control Valve (Ripper Lower)
(4) Passage to Ripper Tip Control Valve (Tip In)
(5) Passage to Ripper Lift Control Valve (Ripper Raise)
(6) Passage to Control Valve for Blade Tilt (Blade Tilt Right)
(7) Passage to Control Valve for Blade Tilt (Blade Tilt Left)
(8) Passage to PCO Valve
(9) Passage to Blade Lift Control Valve (Blade Raise)
(10) Oil Passage for Pilot Supply Oil from the Pilot Filter and from the Pressure Reducing Manifold
(11) Drain Passage from the Pressure Reducing Manifold
(12) Passage to Tank
(13) Solenoid Valve for Blade Raise ("DR")
(14) Solenoid Valve for Engine Overspeed or PCO Valve ("RV")
(15) Solenoid Valve for Blade Tilt (Tilt Left) ("TL")
(16) Solenoid Valve for Blade Tilt (Tilt Right) ("TR")
(17) Solenoid Valve for the Ripper (Ripper Raise) ("RU")
(18) Solenoid Valve for the Ripper (Tip In) ("TI")
(19) Solenoid Valve for the Ripper (Ripper Lower) ("RD")
(20) Solenoid Valve for the Ripper (Tip Out) ("TO")
(21) Solenoid Valve for Blade Lower ("DL") The electrohydraulic pilot manifold receives filtered oil at pilot pressure from the pressure reducing valve and the pilot filter. The electrohydraulic pilot manifold contains eight proportional solenoid valves that receive PWM signals from the implement ECM for operating the blade and ripper, plus a ninth solenoid valve that is used for engine overspeed protection ("PCO valve"). Refer to Illustration 1. Each solenoid includes a pressure tap for checking pilot pressure to the corresponding spool.When the blade is raised or the blade is lowered, the movement of the solenoid plunger is proportional to the electrical current that is sent from the implement ECM. The solenoid plunger determines the amount of oil pressure that is sent to the blade control valve or the ripper control valve. An increase in current will cause an increase in oil pressure in order to move the spool. The electrical current that is sent by the implement ECM to the solenoid is proportional to the amount of movement of the blade control lever.The implement ECM sends only high current signals to the solenoid valves for blade tilt and the ripper solenoid valves. These valves are used only as ON/OFF valves.When the PCO valve is energized by the engine ECM, engine overspeed protection is provided. When the PCO valve is energized by the engine ECM, pilot oil is directed to the shuttle valve in the blade control valve. The shuttle valve will shift. The shuttle valve will then direct high-pressure implement pump oil to the end of the dump valve. The dump valve will shift. The dump valve will then shut off the flow of oil to the hydraulic tank. This situation increases the load on the implement pump. This then increases the load on the engine.When the operator requests a ripper function, the PCO valve is energized by the implement ECM. The PCO valve again directs pilot oil in order to shift the shuttle valve in the blade control valve. This will