JLG 400CRT ANSI Service Manual - Manual (Page 43)

SECTION 3 - TROUBLESHOOTING
3121111 – JLG Lift – 3-1
SECTION 3. TROUBLESHOOTING
3.1 GENERAL
This section contains troubleshooting information to be
used for locating and correcting most of the operating
problems which may develop in the aerial platform. If a
problem should develop which is not presented in this
section or which is not corrected by listed corrective
actions, technically qualified guidance should be obtained
before proceeding with any maintenance.
Troubleshooting and maintenance information pertaining
to the prime mover (engine/motor) that are not contained
in this manual are contained in the applicable engine
maintenance manual.
3.2 TROUBLESHOOTING INFORMATION
The troubleshooting procedures applicable to the aerial
platform are listed and defined in Tables 3-1 through 3-4.
As an aid to table use, the platform sizzor is divided into 4
major groups, each covered separately within this section.
These groups are as follows: Platform, chassis, hydraulic
system and electrical system.
Each malfunction within an individual group or system is
followed by a listing of probable causes which will enable
determination of the applicable remedial action. The prob-
able causes and remedial action should, where possible,
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 machine groups, only those problems which
have more than one probable cause and remedy are
included. This means that problems for which the proba-
ble 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 electrically controlled is to determine
if the circuit is lacking hydraulic oil and electrical power.
This can be ascertained by overriding the bypass valve
(mechanically or electrically) so that oil is available to the
function valve, then overriding the function valve mechani-
cally. If the function performs satisfactorily, the problem
exists with the control circuit.
3.3 HYDRAULIC CIRCUIT CHECKS
The first reference for improper function of a hydraulic sys-
tem, where the cause is not immediately apparent, should
be the troubleshooting chart. The best place to begin the
problem analysis is at the power source (pump) Once it is
determined that the pump is serviceable, then a system-
atic check of the circuit components, beginning with the
control, would follow. For aid in troubleshooting, refer to
the Illustrated Parts Manual for hydraulic diagram of the
various circuits.