GEAR-SUN 3T1064 - Caterpillar

Electric Lowering Control Pump (If Equipped)
When there is a loss of hydraulic power, the load control valve on the telescoping cylinder locks oil in the cylinder in order to prevent the boom from retracting. Refer to Systems Operation, Testing and Adjusting, "Load Control Valves (Lock)" for information on the operation of the load control valve. When this happens the boom can be retracted by manually opening the lock valve on the telescoping cylinder and by manually opening the implement control valve for the telescoping cylinder. The oil is then free to flow from the head end of the cylinder and the cylinder will retract under the weight of the load. Refer to Operation and Maintenance Manual for more information.Note: The boom on the TH580B can not be retracted or lowered by gravity. When the angle of the boom is below approximately 20 degrees, the deflection of the second stage of the boom may prevent the boom from fully retracting. In this situation, the boom can be retracted provided that the machine is equipped with an electric lowering control pump.The electric motor and the pump are directly connected by hydraulic hoses to the telescoping cylinder and to the load control valve for the telescoping cylinder. The pump provides the following functionality:
Allow a means of retracting the boom when the boom will not retract under gravity.Retracting the Boom
Illustration 1 g01194990
Hydraulic Schematic for retracting the boomPress toggle Switch (13) toward the rear of the machine. The motor (14) will activate. The motor turns pump (15) . The oil passes from pump (15) through line (11) past check valve (10A) . Since the solenoid for sequence valve (9) is not energized, the oil from the pump continues through the sequence valve and past check valve (6) . The pump pressure opens lock valve (1) .