JLG 340AJ Service Manual - Manual (Page 133)

SECTION 4 - BOOM & PLATFORM
3121259 – JLG Lift – 4-1
SECTION 4. BOOM & PLATFORM
4.1 PLATFORM CONTROL ENABLE SYSTEM
The platform controls use a time dependent enable circuit to
limit the time availability of "live" or enabled controls. When
the footswitch is depressed, the controls are enabled and the
operator has 7 seconds to operate any control. The controls
will remain enabled as long as the operator continues to use
any function and will remain enabled 7 seconds after the last
function has been used. While the controls are "live", the
enabled light will be illuminated in the platform display panel.
When the time limit has been reached, the enabled light will
turn off and the controls will be disabled. To continue use of
the machine the controls must be re-enabled to start the timer
system over again. This is done by releasing all functions, then
releasing and re-depressing the footswitch.
4.2 TRANSPORT POSITION SENSING SYSTEM
The transport position sensing system uses the two main
boom angle switches (mounted on the upper upright at the
lift cylinder pivot bushing) and the tower boom angle switch
(mounted between the turntable sides at the lower boom link
pivot bushing) to sense when the boom is in the position asso-
ciated with high speed travel. These switches are normally
closed and unactuated when in the transport position. Above
transport angle is recognized when the main boom travels
from the stowed position to 2° above horizontal (it resets at
2.5° below horizontal) or when the tower boom is sensed to be
more than 6.5° above horizontal (it resets at 3.5°). The main
boom may be telescoped to any position, and the articulating
jib may be in any position without changing the transport
state.
This system is used to control the following systems:
• Above Elevation - Drive Speed Cutback System
• Drive/Steer - Boom Function Interlock System (CE Only)
4.3 BOOM MAINTENANCE
Disassembly of the Main Boom
1. Loosen the wear pad retaining bolts at the rear of fly
boom section and remove the shims and wear pads not-
ing the location and amount of shims to aid in reassem-
bly.
2. Using a portable power source, attach hose to telescope
cylinder port block. Using all applicable safety precau-
tions, activate hydraulic system and extend cylinder to
gain access to cylinder rod retaining pin. Shut down the
portable power source.
3. Carefully disconnect hydraulic hose from retract port of
cylinder. There will be initial weeping of hydraulic fluid
which can be caught in a suitable container. After initial
discharge, there should be no further leakage from the
retract port. Cap or plug all openings.
NOTE: When removing the retaining pin from the rod end of the
telescope cylinder, make sure the cylinder is properly sup-
ported.