CP56, CS56, CP64, CS64, CP74 and CS74 Vibratory Soil Compactors Machine Systems Vibratory System Troubleshooting Caterpillar

Vibratory System Troubleshooting
1.1. Operational Checks
2.1. Probable Causes of Vibratory System Problems
3.1. Vibratory Electrical Circuit

------ WARNING! ------

Do not operate or work on this machine unless you have read and understand the instructions and warnings in the Operation and Maintenance Manual. Failure to follow the instructions or heed the warnings could result in injury or death. Contact your AVSpare dealer for replacement manuals. Proper care is your responsibility.

------ WARNING! ------

Escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing 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.

------ WARNING! ------

Personal injury can result from rotating and moving parts. Stay clear of all rotating and moving parts.

Never attempt adjustments while the machine is moving or the engine is running unless otherwise specified.

The machine must be parked on a level surface and the engine stopped.

Attach a "Do Not Operate" or similar warning tag to the start switch and controls before servicing, repairing, or making adjustments to the machine.

------ WARNING! ------

Personal injury or death can result from sudden machine movement.

Sudden movement of the machine can cause injury to persons on or near the machine.

To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine.

------ WARNING! ------

Personal injury can result from hydraulic oil pressure and hot oil.

Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system.

Make sure all of the attachments have been lowered, and the oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.


Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the machine. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.

Refer to Special Publication, NENG2500, "AVSpare Tools and Shop Products Guide", for tools and supplies suitable to collect and contain fluids in AVSpare machines.

Dispose of all fluids according to local regulations and mandates.

Operational Checks

Note: Operate the machine in each direction and in all speeds. Note the noises that are not normal and find the sources of the noises. If the machine is not operating correctly, refer to the list of problems and probable causes below.

Probable Causes of Vibratory System Problems


The vibration system does not work in high amplitude or low amplitude.

Probable causes

  • Fuse failure.

  • The vibratory on/off control switch on the propel control lever has failed.

  • The amplitude selector on the control console has failed.

  • The electrical circuit has a fault.

  • The alternator has failed.

  • Low charge oil pressure.

  • The solenoid valve on the vibratory pump has failed.

  • Mechanical failure of the vibrator mechanism


Low charge oil pressure.

Probable Cause

  • There is a low oil level in the hydraulic tank.

  • The hydraulic filter element is restricted.

  • There is excessive case leakage in the pump and/or the motor.


There is periodic loss of vibration in HIGH range or LOW range.

Probable Cause

  • There is a loose connection in the electric circuit wiring.

  • The vibratory on/off control switch is faulty.

  • The vibratory amplitude selector is faulty.

  • There is a malfunction of the vibratory mechanism.


Slow stopping of the vibratory frequency.

Probable Cause

  • The swashplate and/or the servo piston is sticking.

  • The diameter of the flow control orifice is too small.

  • The main relief valve does not close completely on the return side circuit.


The compactor will not reach maximum vibration frequency.

Probable Cause

  • The frequency gauge is not correctly adjusted or the gauge is faulty.

  • Engine high idle is not correct.

  • The adjustment of the stop in the pump servo is not correct.

  • The oil level in the eccentric weight housing is too high.

  • The high pressure relief valves are set too low.

  • Low charge pressure.

  • The shuttle valve in the vibratory motor is sticking.


The vibratory mechanism is noisy.

Probable Cause

  • The lubrication oil in the vibrator housing is low.

  • Loose retaining bolts for the piston motor.

  • The vibrator shaft bearings have failed.


The hydraulic oil in the circuit overheats.

Probable Cause

  • The hydraulic cooler, the air conditioner condenser, and/or the radiator is restricted.

  • Low charge pressure.

  • Charge oil flow is low.

  • The thermal bypass valve is faulty.

  • The main relief valve is open.

  • An incorrect type of oil is used in the hydraulic system.

Vibratory Electrical Circuit

The vibratory system is engaged by pressing the ON/OFF control switch (button) on the propel control lever. The vibratory system does not operate unless the control switch for the throttle is in the HIGH position.


The Vibratory system does not engage.

Probable Cause

  • The vibratory fuse is blown.

  • Vibratory ON/OFF control switch has failed in the open position.

  • The switch for the throttle control has failed.

  • The switch for the vibratory amplitude control has failed.

  • The vibratory control solenoid has failed.

  • An open circuit exists in the harness for the vibratory system.