AD22 Underground Articulated Truck Hydraulic System Caterpillar

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Hot oil and hot components can cause personal injury. Do not allow hot oil or hot components to contact the skin.

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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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Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine. In order to prevent possible injury, perform the following procedure before testing and adjusting any of the machine hydraulic systems.

The Hoist System Operates Slowly.

Possible Causes

• The oil level is not correct

• The oil is not at the correct operating temperature

• There is a problem with the electrical connections between the hoist control, the Machine ECM, and the Pilot control actuators

• The pilot pressure to the hoist control valve is incorrect

• There is a problem with the hoist control valve

• The spool is not moving to the correct position. This condition could be due to damage or contamination within the hoist control valve or the pilot control actuators

• There is a problem with the piston pumps for the hoist

• There is mechanical damage to one or both of the hoist cylinders. This situation could include damage to the seals

• The body is overloaded

There is no Response when the RAISE Position is Selected or the LOWER Position is Selected.

Possible Causes

• There is a problem with the electrical connections between the hoist control, the Machine ECM, and the Pilot control actuators

• The pilot pressure to the hoist control valve is incorrect

• There is a problem with the hoist control valve. The spool is not moving to the correct position. This condition could be due to damage or contamination within the hoist control valve or the pilot control actuators

• There is mechanical damage to one or both of the hoist cylinders. This situation could include damage to the seals

The Truck Body or will not Maintain the Raised Position

Possible Causes

• There is a problem with the electrical connections between the hoist control, the Machine ECM, and the pilot control actuators

• There is a problem with the hoist control valve. The spool is not moving to the correct position. This situation could be due to damage or contamination within the hoist control valve or the pilot control actuators. The springs, which move the spool to the HOLD position, are damaged

• There is mechanical damage to one or both of the hoist cylinders. This condition could include damage to the seals

Ejector Body Machines

The ejector plate moves slowly or the ejector plate stops when the ejector control is in the EJECT position.

Possible Causes

• The oil level is no not correct

• The oil is not at the correct operating temperature

• The ejector plate is binding. This could be caused by a piece of material or by mechanical damage to the ejector plate or the guides

• The body is overloaded

• There is a problem with one of the electrical connections between the ejector control, the Machine ECM, and the hoist proportioning solenoids. The position sensor that is on the hoist control may also be malfunctioning

• There is a problem with the ejector pressure relief valve for the hoist system.

• There is a problem with the hoist control valve

• There is a problem with the piston pumps

• There is mechanical damage to the ejector cylinder. This could include damage to the seals

• There is a problem with the eject sequence valve

• The implement and steering solenoid valve is not activating because of an electrical fault

The ejector plate moves slowly or the ejector plate stops when the ejector control is in the RETRACT position.

Possible Causes

• The oil level is no not correct

• The oil is not at the correct operating temperature

• The ejector plate is binding. This could be caused by a piece of material or by mechanical damage to the ejector plate or the guides

• There is a problem with one of the electrical connections between the ejector control, the Machine ECM, and the pilot control actuators

• The pilot pressure to the hoist control valve is incorrect

• There is a problem with the hoist control valve

• The spool is not moving to the correct position. This condition could be due to damage or contamination within the hoist control valve or the pilot control actuators

• There is a problem with the piston pumps

• There is mechanical damage to the ejector cylinder. This could include damage to the seals

• There is a problem with the eject sequence valve

• The implement and steering solenoid valve is not activating because of an electrical fault

The tailgate does not operate.

Note: The following information assumes that the tailgate will not open when you attempt to eject material from the body.

Possible Causes

• The retaining pins have not been removed

• The opening pressure of the tailgate is set too low for the load that is being ejected

• There is mechanical damage to one or both of the tailgate cylinders. This could include damage to the seals

• The implement and steering solenoid valve is not activating because of an electrical fault