JLG 15/20MSP Service Manual - Manual (Page 121)

SECTION 6 - TROUBLESHOOTING
3121231 – JLG Lift – 6-1
SECTION 6. TROUBLESHOOTING
6.1 GENERAL
This section contains troubleshooting information to be used for locating and correcting most operating problems. If a prob-
lem 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.
IT IS A GOOD PRACTICE TO AVOID PRESSURE-WASHING ELECTRICAL/ELECTRONIC COMPONENTS. SHOULD PRESSURE-WASHING BE
UTILIZED TO WASH AREAS CONTAINING ELECTRICAL/ELECTRONIC COMPONENTS, JLG INDUSTRIES, INC. RECOMMENDS A MAXIMUM
PRESSURE OF 750 PSI (52 BAR) AT A MINIMUM DISTANCE OF 12 INCHES (30.5 CM) AWAY FROM THESE COMPONENTS. IF ELECTRICAL/
ELECTRONIC COMPONENTS ARE SPRAYED, SPRAYING MUST NOT BE DIRECT AND BE FOR BRIEF TIME PERIODS TO AVOID HEAVY
SATURATION.
6.2 TROUBLESHOOTING INFORMATION
Troubleshooting procedures applicable to this machine are listed and defined starting with Section 6.8, TROUBLESHOOT-
ING TABLES Index in this section of the manual.
Each malfunction within an individual group or system is followed by a listing of probable causes which will enable determi-
nation of the applicable remedial action. The probable causes and the remedial action should, where possible, be checked
in the order listed in the troubleshooting tables.
It should be noted that there is no substitute for a thorough 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 electri-
cal 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 hydraulically operated and electrically controlled is to determine if the cir-
cuit is lacking hydraulic oil and electrical control power. This can be ascertained by overriding the bypass valve (mechani-
cally 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.
6.3 HYDRAULIC CIRCUIT CHECKS
(SEE FIGURE 6-8.)
The first reference for improper function of a hydraulic system, where the cause is not immediately apparent, should be the
Hydraulic Diagram Circuit. The best place to begin the problem analysis is at the power source (pump). Once it is deter-
mined that the pump is serviceable, then a systematic check of the circuit components, would follow.
NOTE: For aid in troubleshooting, refer to Figure 6-8. for HYDRAULIC DIAGRAM circuit.
6.4 ELECTRICAL CIRCUIT CHECKS
General
The drive system on the MVL and MSP machines requires a microprocessor controlled electrical circuit to operate smoothly
and accurately. All platform control console functions are relayed to various machine components (i.e. platform up/down,
drive functions, etc.) through the Ground Control Module microprocessor box (mounted at the rear of the machine). The
Ground Control Module is pre-programmed with factory pre-set personality settings for each machine function.
To help diagnose any problems with components plugged into the Ground Control Module, the module is designed with an
internal fault code and text messaging system displayed on an LCD screen at the module. The platform control console also
will display LED Flash Codes using the LED strip at the top of the console. When operating normally the LED panel on the
platform control console indicates the battery voltage status using ten (10) LEDs (red/yellow/green). If a malfunction to the