Item
Description
Action
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 pressure limiters and high pressure relief
valves and adjust or 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.
Integral Filter Bypass
Item
Description
Action
Filter bypass activated
Filter is plugged causing fluid to bypass filter.
Replace filter. Check that bypass switch indicates proper
operation after filter is replaced.
Filter bypass indicator switch Filter bypass indicator switch is indicating wrong bypass
situation.
Check/replace switch.
open>=510 ohms
closed<=122 ohms
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.
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. If neutral is still impossible
to set, balance the swashplate (see Mechanical Neutral
Adjustment). If you still cannot set neutral, replace the
control.
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.
Pump control orifices
Control orifices are blocked.
Clean control orifices.
Pump control screens
Control screens are blocked.
Replace control screens. Only a Danfoss Authorized Service
Center may remove the unit’s endcap without voiding the
warranty.
Bypass function open
If bypass function is open, the system loop will be
depressurized.
Close bypass valves. Replace high pressure relief valve if
defective.
Low charge pressure with
pump in neutral
Low charge pressure insufficient to recharge system loop.
Measure charge pressure with the pump in neutral. If
pressure is low, go to Pump charge relief valve.
Low charge pressure with
pump in stroke
Low charge pressure resulting from elevated loop leakage.
Insufficient control pressure to hold pump in stroke.
Deadhead the pump to isolate it from the motor.With
pump in partial stroke and engaged for only a few seconds,
check pump charge pressure. Low charge pressure
indicates a malfunctioning pump. Continue to next step.
Good charge pressure indicates a malfunctioning motor or
other system component. Check motor charge relief
operation (if present).
Service Manual
H1 Pumps 069/078, 089/100, 115/130, 147/165, 210/250
Troubleshooting
28 |
©
Danfoss | May 2018
520L0848 | AX00000087en-US0308
