Item
Description
Action
Pump charge relief valve
A pump charge relief valve that is leaky, contaminated, or
set too low will depressurize the system.
Adjust or replace pump charge relief valve as necessary.
Charge pump inlet filter
A clogged filter will under supply system loop.
Inspect filter and replace if necessary.
Charge pump
A malfunctioning charge pump will provide insufficient
charge flow.
Repair or replace the charge pump.
System pressure
Low system pressure does not provide enough power to
move load.
Measure system pressure. Continue to next step.
High pressure relief or
pressure limiter valves
Defective high pressure relief or pressure limiter valves
cause system pressure to be low.
Repair or replace high pressure relief or pressure limiter
valves.
Input to control
Input operating improperly
Repair/replace control.
System Noise or Vibration
Item
Description
Action
Reservoir oil level
Low oil level leads to cavitation.
Fill reservoir.
Aeration of the oil/pump
inlet vacuum
Air in system decreases efficiency of units and controls.
Excessive noise, foaming oil, and hot oil all indicate air in
system.
Find location where air is entering into the system and
repair. Check that inlet line is not restricted and is proper
size.
Cold oil
If oil is cold, it may be too viscous for proper function and
pump cavitates.
Allow the oil to warm up to its normal operating
temperature with engine at idle speed.
Pump inlet vacuum
High inlet vacuum causes noise/cavitation.
Check that inlet line is not restricted and is of proper size.
Check filter and bypass switch.
Shaft couplings
A loose shaft coupling will cause excessive noise.
Replace loose shaft coupling..
Shaft alignment
Misaligned shafts create noise.
Align shafts.
Charge/system relief valves
Unusual noise may indicate sticking valves and possible
contamination.
Clean/replace valves and test pump.
Sluggish System Response
Item
Description
Action
Oil level in reservoir
Low oil level causes sluggish response.
Fill reservoir.
High pressure relief valves/
pressure limiter settings
Incorrect pressure settings affects system reaction time.
Adjust or replace high pressure relief valves.
Low prime mover speed
Low engine speed reduces system performance.
Adjust engine speed.
Charge pressure
Incorrect pressure affects system performance.
Measure and adjust charge pressure relief or replace charge
pump.
Air in system
Air in system produces sluggish system response.
Fill tank to proper level. Cycle system slowly for several
minutes to remove air from system.
Contaminated control
orifices
Control orifices are plugged.
Clean control orifices.
Contaminated control
screens
EDC supply screen is plugged.
Replace control screens. Only a Danfoss Authorized Service
Center may remove the unit’s endcap without voiding the
warranty.
Pump inlet vacuum
Inlet vacuum is too high resulting in reduced system
pressure.
Measure charge inlet vacuum. Inspect line for proper sizing.
Replace filter. Confirm proper bypass operation.
Service Manual
H1 Pumps 069/078, 089/100, 115/130, 147/165, 210/250
Troubleshooting
©
Danfoss | May 2018
520L0848 | AX00000087en-US0308 | 29