Troubleshooting; Overview; System Operating Hot; Transmission Operates Normally In One Direction Only - Danfoss LDT 21 Service Manual

Service Manual
LDT 21/24/32 Closed Circuit Axial Piston Transmission

Troubleshooting

Overview

System Operating Hot

Item Description
Oil level in reservoir. Insufficient hydraulic fluid does not meet cooling demands
of system.
Heat exchanger. Heat exchanger is not sufficiently cooling
the system.
System relief pressure If the system relief valves are worn, contaminated, or valve
settings settings are too low, the relief valves get overworked.
System pressure. Frequent or long term operation over system relief setting
creates heat in system.

Transmission Operates Normally in One Direction Only

Item Description
Control linkage Control linkage is operating improperly.
Interchange charge check/ Interchanging the charge check/HPRVs will show if the
HPRVs problem is related to the valve function.

System will not Operate in Either Direction

Item Description
Oil level in reservoir Insufficient hydraulic fluid to supply system loop.
Charge pressure with pump Low charge pressure insufficient to recharge system loop
in neutral
System pressure Low system pressure does not provide enough power to
move load.
Charge check/HPRVs Low system pressure does not provide enough power to
move load.
Control linkage Linkage operating improperly.

System Noise or Vibration

Item Description
Reservoir oil level Low oil level leads to cavitation.
Aeration of the oil/charge Air in the system decreases efficiency of units and controls.
inlet vacuum Air in the system is indicated by excessive noise in HST,
foaming in oil, and hot oil.
Cold oil If oil is cold, it may be too viscous for proper function and
pump cavitates
Charge inlet vacuum High inlet vacuum causes noise/cavitation.
Shaft couplings A loose shaft coupling causes excessive noise.
Shaft alignment Misaligned HST and prime mover shafts create noise.
Charge check/HPRVs Unusual noise may indicate sticking valves. Possible
contamination.
© Danfoss | June 2022
This section provides general steps to follow if you observe undesirable system conditions. Follow the
steps listed until you solve the problem. Some of the items are system specific. We reference the section
in this manual of more information is available. Always observe the safety precautions listed in the
Introduction section and any precautions related to your specific equipment.
Action
Fill reservoir to proper level.
Check air flow and input air temperature
for heat exchanger. Clean, repair or
replace heat exchanger.
Verify settings of high pressure relief valves
and adjust or replace as necessary.
Measure system pressure. If pressure
is too high, reduce loads.
Action
Repair/replace linkage
If the problem changes direction, replace the defective
valve.
Action
Fill reservoir to proper level.
Measure charge pressure with the pump in neutral. If
pressure is low, go to next step.
Measure system pressure. Continue to next step.
Repair or replace charge check/HPRVs
Repair/replace linkage
Action
Fill reservoir.
Find location where air is entering into the system and
repair. Check that inlet line is not restricted and is proper
size.
Allow the oil to warm up to its normal operating
temperature with engine at idle speed.
Check that inlet line is not restricted and is proper size.
Check filter.
Replace loose shaft coupling.
Align shafts.
Clean/replace valves and test the unit.
AX417167456877en-000101 | 19