Neutral difficult or impossible to find
Item Description Action
Input to pump control Input to control module is operating improperly. Disconnect input and check to see if pump comes back to
neutral. If Yes, input fault, replace/repair external controller.
If No, go to next step.
Pump control neutral Neutral set improperly. Shunt servo gauge ports M4 and M5 together with external
hose and see if pump comes back to neutral. If Yes: control
neutral improperly set (see Control Neutral Adjustment on
page 40). If no: balance swashplate (see Mechanical
neutral adjustment on page 42). If you still cannot set
neutral, replace control.
System operating hot
Item Description Action
Oil level in reservoir Insufficient hydraulic fluid will not meet
cooling demands of system.
Fill reservoir to proper level.
Heat exchanger Heat exchanger not sufficiently cooling
the system.
Check air flow and input air temperature
for heat exchanger. Clean, repair or
replace heat exchanger.
Charge pressure Low charge pressure will overwork system. Measure charge pressure. Inspect and
adjust or replace charge relief valve. Inspect charge pump.
Repair or replace charge pump.
Charge pump inlet vacuum High inlet vacuum will overwork system. A dirty filter will
increase the inlet vacuum. Inadequate line size will restrict
flow.
Check charge inlet vacuum. If high,
inspect inlet filter and replace as necessary.
Check for adequate line size, length
or other restrictions.
System relief pressure
settings
If the system relief valves are worn, contaminated, or valve
settings are too low, the relief valves will be overworked.
Verify settings of high pressure relief valves and replace
valves as necessary.
System pressure Frequent or long term operation over system relief setting
will create heat in system.
Measure system pressure. If pressure
is too high, reduce loads.
Transmission operates normally in one direction only
Item Description Action
Input to pump control Input to control module is operating improperly. Check control input and repair or replace as necessary.
Control orifices Control orifice(s) are blocked. Clean control orifices.
Control screens Control screen(s) are blocked. Clean or replace control screens.
Interchange charge check /
HPRVs
Interchanging the charge check / HPRVs will show if the
problem is related to the valve function.
If the problem changes direction, replace the valve that
does not operate correctly.
Servo pressure Servo pressure low or decaying. Check for damaged servo seals. Replace and retest. Refer to
520L0928 H1 45/53 Tandem Repair Instructions for seal
locations. Only a Danfoss Global Service Partner may
remove the servo piston without voiding the warranty.
System will not operate in either direction
Item Description Action
Oil level in reservoir Insufficient hydraulic fluid to supply system loop. Fill reservoir to proper level.
Control orifices Control orifices are blocked. Clean control orifices.
Control screens Control screens are blocked. Clean or replace control screens.
Service Manual
H1 45/53/60/68 Tandem Closed Circuit Axial Piston Pumps
Troubleshooting
30 |
©
Danfoss | June 2018 520L0928 | AX00000103en-US0303
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