JLG 15ELI Service Manual - Manual (Page 35)

SECTION 3 - TROUBLESHOOTING
3120779 – 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.
3.2 TROUBLESHOOTING INFORMATION
The troubleshooting procedures applicable to the aerial
platform are listed and defined in Table 3-1., AC Unit Trou-
bleshooting and Table 3-2., DC Unit Troubleshooting.
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 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 machine groups, only those problems which
are symptomatic of greater problems which have more
than 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 electrically controlled is to determine
if the circuit is lacking hydraulic oil and electrical control
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
mechanically. If the function performs satisfactorily, the
problem exists with the control circuit.
3.3 ELECTRICAL AND HYDRAULIC CIRCUIT
CHECKS
(See Figure 3-1., 3-2., 3-3., 3-4. & 3-5.)
The first reference for improper function of a electrical/
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 power source
(pump). Once it is determined that the pump is service-
able, then a systematic check of the circuit components,
beginning with the control, would follow.
NOTE: For aid in Hydraulic troubleshooting, refer to Figure
3-1. HYDRAULIC Schematic at the end of this sec-
tion. For ELECTRICAL Diagrams refer to Figure 3-2.,
3-3., 3-4. & 3-5., also at the end of this chapter.