Danfoss LDU21C Service Manual page 21

Service Manual
LDU21C Closed Circuit Axial Piston Transmission
Troubleshooting
Item Description
Shaft alignment Misaligned HST and prime mover shafts create noise.
Charge check/HPRVs Unusual noise may indicate sticking valves. Possible
contamination.
Sluggish System Response
Item Description
Oil level in reservoir Low oil level causes sluggish response.
Charge check/HPRVs Incorrect pressure settings affects system reaction time.
Low prime mover speed Low engine speed reduces system performance
Air in system Air in system produces sluggish system response
Charge inlet vacuum Inlet vacuum is too high resulting in reduced system
pressure.
Control linkage Linkage operating improperly
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Danfoss | April 2025
Action
Align shafts.
Clean/replace valves and test the unit.
Action
Fill reservoir.
Replace charge check/HPRVs
Adjust engine speed.
Fill tank to proper level. Cycle system slowly for several
minutes to remove air from system.
Measure charge inlet vacuum. Inspect line for proper sizing.
Replace filter. Confirm proper bypass operation.
Repair or replace control linkage
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