JLG 24RS Service Manual - Manual (Page 157)

SECTION 5 - HYDRAULICS
3121287 – JLG Lift – 5-33
Table 5-3. Transmission Operates Normally in One Direction Only
Item Description Action
Open bypass valves. Open bypass causes one or both directions to be inopera-
tive. 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.
Control screens Control screen(s) are blocked. Clean or replace control screens.
Pressure limiters Malfunctioning pressure limiter can affect one direction
while the other functions normally. Exchange pressure limiters. If the problem changes direction, replace the valve
that does not operate correctly. Remember to return the PLs to their original
position afterward. Settings may be different for forward/ reverse.
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 520L0957 H1
45/53/06/68 Repair instructions for seal locations. Only a Sauer-Danfoss
Global Service Partner may remove the servo piston without voiding the war-
ranty.
Table 5-4. 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.
Pump control screens Control screens are blocked. Clean control screens. Refer to 520L0957 H1 45/53/60/68 Repair instructions
for screen locations. If pump is being repaired for warranty evaluation, repair
must be done by a Sauer-Danfoss Global Service Partner.
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 contami-
nated, 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 leak-
age, 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.
System pressure Low system pressure does not provide enough power to
move load. Measure system pressure. Continue to next step.
System relief valves Defective high pressure relief or pressure limiter valves
cause slow system pressure. Repair or replace high pressure relief or pressure limiter valves.
Input to control Input is operating improperly. Repair/replace control.