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 is 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
Open bypass valves.
Open bypass causes one or both directions to be
inoperative.
Close/repair bypass function.
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.
High pressure relief valves
(HPRV)
Malfunctioning HPRV can affect one direction while the
other functions normally.
Exchange HPRVs. If the problem changes direction, replace
the valve that does not operate correctly. Remember to
return HPRVs to their original position afterward. Settings
may be different for forward/reverse.
Servo pressure
Servo pressure low or decaying.
Check for torn/missing servo seals. Replace and retest.
Refer to AX00000303 MP1 Repair Instructions for seal
locations. Only a Danfoss Global Service Partner may
remove the servo piston without voiding the warranty.
System Does 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.
Open bypass valve
If bypass valves are open, the system loop becomes
depressurized.
Close bypass valves. Replace high pressure relief valve if
defective.
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 next step.
Pump charge relief valve
A pump charge relief valve that is leaky, or contaminated,
or set too low depressurizes the system.
Adjust or replace pump charge relief valve as necessary.
Charge pressure with pump
in stroke
Low charge pressure, resulting from elevated loop leakage,
is insufficient control pressure to hold pump in stroke.
Isolate pump from motor. With pump in partial stroke and
engaged for only a few seconds, check pump charge
pressure. Low charge pressure indicates a malfunctioning
pump. Good charge pressure indicates a malfunctioning
motor or other system component. Check motor charge
relief operation (if present).
Charge pump inlet filter
A clogged filter under supplies system loop.
Inspect filter and replace if necessary.
Charge pump
A malfunctioning charge pump provides insufficient charge
flow.
Repair or replace the charge pump.
Service Manual
MP1
Troubleshooting
44 |
©
Danfoss | April 2019
AX00000244en-000201
