JLG 1250AJP Service Manual - Manual (Page 378)

SECTION 5 - HYDRAULICS
5-24 – JLG Lift – 3121171
5.3 COUNTERBALANCE VALVE CHECK
1. Position the machine on a firm level surface.
2. Ensure the tower boom and main booms are on
their respective boom rests.
3. Swing the turntable to the side about 35-45° to gain
access to the counterbalance valve.
4. Access the Tower Lift Cylinder Counterbalance Valve
through the access hole in the bottom plate of the
turntable.
5. Torque the counterbalance valve 45 to 50 foot
pounds (61 to 68 Nm) and take note of how much
the counterbalance valve moves.
6. If the valve moves less than 0.125" (3 mm) radially
(see example below), proceed to the next step. If the
valve moves more than 0.125" (3 mm) radially (see
sketch below), replace the counterbalance valve,
proceed to Step #8.
7. After applying the torque to the valve, examine the
valve for hydraulic oil leaks. If the valve leaks,
replace the counterbalance valve, see Step #10. If
the valve does not leak, proceed to Step #13.
8. To replace the counterbalance valve:
a. Remove the valve cartridge.
b. Examine the removed cartridge for complete-
ness of the valve, the o-rings and seals.
c. If the valve, seals and o-rings are complete and
accounted for, proceed to the next step.
d. If any portion of the valve, o-rings or seals are
missing, quarantine the machine. Do NOT allow
the tower boom to be raised. Contact a certified
service technician and make sure the missing
parts are accounted for.
IF THE CARTRIDGE REQUIRES REPLACEMENT, THE PORT IN THE
VALVE BLOCK MUST BE FREE OF RESIDUAL HYDRAULIC OIL
BEFORE INSTALLING THE NEW CARTRIDGE OR THE CARTRIDGE
SEALS MAY BE DAMAGED DURING INSTALLATION.
9. Inspect the new counterbalance valve for complete-
ness of the valves, o-rings and seals.
10. Carefully install the new counterbalance valve into
the valve block and torque 45 to 50 foot pounds (61
to 68 Nm).
11. Return the machine to the stowed position.
1/8”
(3 mm)