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Troubleshooting
Bosch Rexroth Corporation
, A21VG Series 10, RE 93223-01-B/09.2020
Table 13: Axial piston unit malfunction table
Malfunction
Possible cause
Remedy
No or insufficient pressure
Faulty mechanical drive
(e.g. defective coupling).
Machine/system manufacturer.
Drive power too low.
Machine/system manufacturer.
Insufficient suction conditions, e.g. air in
the suction line, insufficient diameter of
the suction line, viscosity of the hydraulic
fluid too high, suction height too high,
suction pressure too low, contaminants
in the suction line (only relevant for the
version with boost pump).
Machine or system manufacturer
(e.g. optimize inlet conditions, use suitable
hydraulic fluid).
Completely air bleed axial piston unit, fill
suction line with hydraulic fluid.
Remove contaminants from the suction
line.
Hydraulic fluid not in optimum viscosity
range.
Use suitable hydraulic fluid (machine/
system manufacturer).
External control of the control device
defective.
Check external control (machine/system
manufacturer).
Insufficient pilot pressure or control
pressure.
Check pilot pressure or control pressure,
contact Bosch Rexroth Service.
Malfunction of the control device or
controller of the axial piston unit.
Contact Bosch Rexroth Service.
Wear of axial piston unit.
Exchange axial piston unit,
contact Bosch Rexroth Service.
Mechanical damage to the axial piston unit
(e.g. bearing damage).
Exchange axial piston unit,
contact Bosch Rexroth Service.
Output unit defective (e.g. hydraulic motor
or cylinder).
Machine/system manufacturer.
Pressure/flow fluctuations
Axial piston unit not or insufficiently air
bled.
Completely air bleed axial piston unit.
Insufficient suction conditions, e.g. air in
the suction line, insufficient diameter of
the suction line, viscosity of the hydraulic
fluid too high, suction height too high,
suction pressure too low, contaminants
in the suction line (only relevant for the
version with boost pump).
Machine or system manufacturer
(e.g. optimize inlet conditions, use suitable
hydraulic fluid).
Completely air bleed axial piston unit, fill
suction line with hydraulic fluid.
Remove contaminants from the suction
line.
Excessive hydraulic fluid temperature and
case temperature
Excessive inlet temperature at the axial
piston unit.
Machine or system manufacturer:
inspect system, e.g malfunction of the
cooler, insufficient hydraulic fluid in the
reservoir.
Malfunction of the pressure control valves
(e.g. high-pressure relief valve, pressure
controller).
Contact Bosch Rexroth Service.
Wear of axial piston unit.
Exchange axial piston unit,
contact Bosch Rexroth Service.
Instability/vibrations
Setpoint value not stable.
Machine/system manufacturer.
Resonance in the reservoir line.
Machine/system manufacturer.
Malfunction of the control devices or the
controller.
Contact Bosch Rexroth Service.
