Danfoss 51 Series Service Manual

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Danfoss 51 Series Service Manual Manual pdf 30 page image

Motor operates normally in one direction onlyCheck Cause Corrective action1. Charge pressure If charge pressure is low in one direction, the loopflushing shuttle spool may be sticking to one side.Measure charge pressure in forward and reverse. Ifpressure drops in one direction, inspect and repairloop flushing shuttle spool.2. Motor control If control shifts motor to minimum displacement inone direction, motor may not have enough torqueto operate.Measure maximum and minimum servo pressures tocheck control operation. Repair control or correctinput signal if necessary.3. Pressure compensator control If pressure compensator operates in one directiononly, the motor will stay at minimum displacementin the other directionCheck brake pressure defeat spool. It may be stickingor receiving an improper signal. Repair spool orcorrect input signal.Improper output speedCheck Cause Corrective action1. Oil level in reservoir Insufficient hydraulic fluid will reduce systemefficiency.Fill reservoir to proper level.2. Threshold setting Improper threshold setting will cause motor tohave wrong displacement for given signal.Check threshold setting. Refer to control servicemanual for adjustment procedure.3. Pressure compensator setting Improper pressure compensator setting shiftsmotor displacement at wrong pressure.Check pressure compensator setting. Adjust ifnecessary.4. Control spool or piston Pressure compensator piston or spool stickingholds motor at wrong displacement.Check pressure compensator piston or spool. Repairor replace if needed.5. Control orifices Blocked or restricted orifice causes motor to shiftimproperly.Remove, inspect, and clean all orifices.6. Control piston Sticky control piston causes motor to shiftimproperly.Check control piston for proper operation. Repair ifnecessary.7. Control input signal Improper input signal causes motor to shiftimproperly.Correct control input signal.8. Internal leakage Excess internal leakage causes lower chargepressure and affects system performance includingoutput speed.Install loop flushing defeat option and monitor caseflow. If case flow is excessive, motor may require majorrepair. Contact your Danfoss Service Provider.Low output torqueCheck Cause Corrective action1. System pressure Low system pressure at motor reduces outputtorque.Measure system pressure at the motor. If the pressurelimiter or relief valve setting is low, increase setting tothe proper level.2. Charge pressure Low loop flushing relief valve setting may causeimproper supply pressure to motor control.Measure charge pressure in forward and reverse.Adjust loop flushing relief valve setting if necessary.3. Pressure compensator setting High pressure compensator setting causesimproper motor displacement for torque required.Check and adjust pressure compensator setting.4. Control orifices Blocked or restricted orifice causes motor to shiftimproperly.Remove, inspect and clean all orifices.5. Pressure compensator piston orspoolSticking pressure compensator piston or spoolcauses control to hold motor at minimumdisplacement.Remove and inspect control spool and sensing piston.Repair or replace if necessary.6. Control spool or piston Sticking 4-way spool or control piston causesmotor to shift improperly.Remove and inspect 4-way spool and control piston.Repair or replace if necessary.7. Two position solenoid Two position control not shifting motor tomaximum displacement.Inspect solenoid valve for bent stem or bad coil.Repair or replace if necessary.Service ManualSeries 51 and 51-1 MotorsTroubleshooting30 | © Danfoss | March 2016 11008567 | AX00000013en-US0202