User Manual

SECTION 3 - TROUBLESHOOTING
3120884 – JLG Lift – 3-1
SECTION 3. TROUBLESHOOTING
3.1 GENERAL
This section con tains troubleshooting info rmation to be
used for locating and correcting most of the operating
problems which may develop. If a problem should
develop which is not presented in this section or which is
not corrected by listed c orrective actio ns, technica lly qual-
ified guidance should be obtained before proceeding with
any maintenance.
3.2 TROUB LESHOOT ING.
The troubleshooting procedures applicable to the aerial
platform are l isted and def ined in Tables 3-1 through 3 -6.
As an aid to table use, the aerial platform is divided into
four major groups, each covered separately within this
section. These groups are as f ollows: elevation system,
chassis assembly, hydraulic system and electrical system.
Each malf unction wi thin an individua l group o r system i s
followed by a listing of probable causes which will enable
determ ination of the appli cable remed ial action . The prob -
able causes and the remedial action should, where possi-
ble, be checked in the order listed in the tables.
It should be noted that there is no substitute for a thor-
ough knowledge of the equipment and related systems.
It should be recognized that the majority of the problems
arising in the machine will be centered in the hydraulic
and electrical systems. For this reason, every effort has
been made to ensure that all likely problems in these
areas are given the fullest possible treatment. In the
remaining machin e groups, only those problems which
are symptomatic of greater problems which have more
that one probable cause and remedy are included. This
means that problems for which the probable cause and
remedy may be immediately obvious are not listed in this
section.
The first rule for troubleshooting any circuit that is hydrau-
lically operated and electric ally controlled is to det ermine
if the cir cuit is lack ing hydra ulic oil and ele ctrical con trol
power. T his can be ascert ained by overri ding the bypass
valve so that oil is available to the function valve, then
overriding th e function valve mechanically. If t he function
performs satisfactorily, the problem exists with the control
circuit.
3.3 HYDRAULIC CIRCUIT CHECKS.
The reference for improper function of a hydraulic system,
where the cause is not immediately apparent, should be
the Troubleshooting Chart. The best place to begin the
problem analysis is at the po wer source (pump). Once i t is
determined that the pump is serviceable, then a system-
atic check of the circuit components, beginning with th e
control, would follow. For aid in troubleshooting, refer to
the Il lustrate d Parts Manual f or hydr aulic diagra ms of the
various circuits
Updated 2-15-00