
Service and Maintenance Manual
Model
12SP
15SP
3120775
June 29, 2018 - Rev K
ANSI


FOREWORD
The purpose of this manual is to provide users with the operating procedures essential for the promotion of
proper machine operation for its intended purpose. It is important to over-stress proper machine usage. All
information in this manual should be READ and UNDERSTOOD before any attempt is made to operate the
machine. YOUR OPERATING MANUAL IS YOUR MOST IMPORTANT TOOL - Keep it with the machine.
REMEMBER ANY EQUIPMENT IS ONLY AS SAFE AS THE OPERATOR.
BECAUSE THE MANUFACTURER HAS NO DIRECT CONTROL OVER MACHINE APPLICATION AND
OPERATION, PROPER SAFETY PRACTICES ARE THE RESPONSIBILITY OF THE USER AND HIS OPER-
ATING PERSONNEL.
ALL INSTRUCTIONS IN THIS MANUAL ARE BASED ON THE USE OF THE MACHINE UNDER PROPER
OPERATING CONDITIONS, WITH NO DEVIATIONS FROM THE ORIGINAL DESIGN. ALTERATION AND/
OR MODIFICATION OF THE MACHINE IS STRICTLY FORBIDDEN, WITHOUT WRITTEN APPROVAL
FROM JLG INDUSTRIES, PER OSHA REGULATIONS.
THIS "SAFETY ALERT SYMBOL" IS USED TO CALL ATTENTION TO POTENTIAL HAZARDS
WHICH MAY LEAD TO SERIOUS INJURY OR DEATH IF IGNORED.
Safety of personnel and proper use of the machine are of primary concern, DANGER, WARNING, CAUTION,
NOTICE, INSTRUCTIONS and NOTE are inserted throughout this manual to emphasize these areas. They
are defined as follows:
JLG INDUSTRIES, INC. MAY HAVE ISSUED SAFETY RELATED BULLETINS FOR YOUR JLG PRODUCT. CONTACT JLG INDUS-
TRIES, INC. OR THE LOCAL AUTHORIZED JLG DISTRIBUTOR FOR INFORMATION CONCERNING SAFETY RELATED BULLE-
TINS WHICH MAY HAVE BEEN ISSUED FOR YOUR JLG PRODUCT. ALL ITEMS REQUIRED BY THE SAFETY RELATED
BULLETINS MUST BE COMPLETED ON THE AFFECTED JLG PRODUCT.
Due to the continuous product improvements, JLG Industries, Inc. reserves the right to make specification changes without
prior notification. Contact JLG Industries, Inc. for updated information.
DANGER INDICATES AN IMMINENTLY HAZARDOUS SITUA-
TION WHICH, IF NOT AVOIDED WILL RESULT IN SERIOUS
INJURY OR DEATH.
CAUTION INDICATES A POTENTIALLY HAZARDOUS SITUA-
TION WHICH, IF NOT AVOIDED, MAY RESULT IN MINOR OR
MODERATE INJURY. IT MAY ALSO BE USED TO ALERT
AGAINST UNSAFE PRACTICES.
Also in this Manual "Notes:" are used to provide infor-
mation of special interest.
WARNING INDICATES A POTENTIALLY HAZARDOUS SITU-
ATION WHICH, IF NOT AVOIDED COULD RESULT IN SERI-
OUS INJURY OR DEATH.
IMPORTANT OR INSTRUCTIONS PROCEDURES ESSENTIAL
FOR SAFE OPERATION AND WHICH, IF NOT FOLLOWED
MAY RESULT IN A MALFUNCTION OR DAMAGE TO THE
MACHINE.

NOTES:

MAINTENANCE SAFETY PRECAUTIONS
3120775 – JLG Lift – a
MAINTENANCE SAFETY PRECAUTIONS
GENERAL
This section contains the general safety precautions
which must be observed during maintenance of the aerial
platform. It is of utmost importance that maintenance per-
sonnel pay strict attention to these warnings and precau-
tions to avoid possible injury to themselves or others or
damage to the equipment. A maintenance program must
be established by a qualified person and must be followed
to ensure that the machine is safe to operate.
MODIFICATION OF THE MACHINE WITHOUT CERTIFICATION BY
A RESPONSIBLE AUTHORITY THAT THE MACHINE IS AT LEAST
AS SAFE AS ORIGINALLY MANUFACTURED IS A SAFETY VIOLA-
TION.
The specific precautions to be observed during machine
maintenance are inserted at the appropriate point in the
manual. These precautions are, for the most part, those
that apply when servicing hydraulic and larger machine
component parts.
Your safety, and that of others, is the first consideration
when engaging in the maintenance of equipment. Always
be conscious of component weight and never attempt to
move heavy parts without the aid of a mechanical device.
Do not allow heavy objects to rest in an unstable position.
When raising a portion of the equipment, ensure that ade-
quate support is provided.
SINCE THE MACHINE MANUFACTURER HAS NO DIRECT CON-
TROL OVER THE FIELD INSPECTION AND MAINTENANCE,
SAFETY IN THIS AREA IS THE RESPONSIBILITY OF THE OWNER/
OPERATOR.
HYDRAULIC SYSTEM SAFETY
1. It should be particularly noted that the machines
hydraulic systems operate at extremely high and
potentially dangerous pressures. Every effort should
be made to relieve any system pressure prior to dis-
connecting or removing any portion of the system.
2. Relieve system pressure by activating the lift DOWN
control with the platform completely lowered to
direct any line pressure back into the return line to
the reservoir. Pressure feed lines to system compo-
nents can then be disconnected with minimal fluid
loss.
MAINTENANCE
FAILURE TO COMPLY WITH SAFETY PRECAUTIONS LISTED IN
THIS SECTION COULD RESULT IN MACHINE DAMAGE, PERSON-
NEL INJURY OR DEATH AND IS A SAFETY VIOLATION.
• REMOVE ALL RINGS, WATCHES, AND JEWELRY
WHEN PERFORMING ANY MAINTENANCE.
• DO NOT WEAR LONG HAIR UNRESTRAINED, OR
LOOSE FITTING CLOTHING AND NECKTIES WHICH
ARE APT TO BECOME CAUGHT ON OR ENTANGLED
IN EQUIPMENT.
• OBSERVE AND OBEY ALL DANGER, WARNING, CAU-
TION AND OTHER INSTRUCTIONS ON MACHINE AND
IN SERVICE MANUAL.
• KEEP STANDING SURFACES AND HAND HOLDS
FREE OF OIL, GREASE, WATER, ETC.
• NEVER WORK UNDER AN ELEVATED PLATFORM
UNTIL PLATFORM HAS BEEN SAFELY RESTRAINED
FROM ANY MOVEMENT BY BLOCKING OR OVER-
HEAD SLING.
• BEFORE MAKING ADJUSTMENTS, LUBRICATING OR
PERFORMING ANY OTHER MAINTENANCE, SHUT
OFF ALL POWER CONTROLS.
• BATTERY SHOULD ALWAYS BE DISCONNECTED
DURING REPLACEMENT OF ELECTRICAL COMPO-
NENTS.
• KEEP ALL SUPPORT EQUIPMENT AND ATTACH-
MENTS STOWED IN THEIR PROPER PLACE.
• USE ONLY APPROVED, NONFLAMMABLE CLEANING
SOLVENTS.

EFFECTIVITY PAGE
b – JLG Lift – 3120775
EFFECTIVITY CHANGES
June 2, 1999 - A - Original Issue of Manual
March 7, 2000 - B - Manual Revised (added CSA/Latin America Specifications)
April 13, 2000 - C - Manual Revised (added 12SP Model)
April 25, 2000 - D - Manual Revised (corrected Mast Disassembly/Assembly - Section-2.)
November 22, 2000 - E - Manual Revised - Pages Affected;Section 2 - Pages 2-4 through 2-19.
January 25, 2001 - F - Manual Revised - Pages Affected;Section 2 - Page 2-14 and 2-15.
January 16, 2002 - G - Manual Revised
January 20, 2006 - H - Manual Revised
July 10, 2006 - I - Manual Revised
March 17, 2008 - J - Manual Revised
June 29, 2018 - K - Revised Covers

3120775 – JLG Lift – i
TABLE OF CONTENTS
SUBJECT - SECTION, PARAGRAPH PAGE NO.
MAINTENANCE SAFETY PRECAUTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a
Hydraulic System Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a
EFFECTIVITY CHANGES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . b
SECTION 1 - SPECIFICATIONS
1.1 CAPACITIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Hydraulic Oil Reservoir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.2 COMPONENT DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Hydraulic Pump/Electric Motor Assembly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Battery Charger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3 PERFORMANCE DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Platform Capacity (Max. Rated Load) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Machine Speeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Machine Weight (With Standard Platform) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Machine Height (Platform Stowed) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Maximum Platform Height (Mast Fully Extended) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Maximum Working Height (Average Person) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Machine Overall Width And Length (Stowed) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.4 TORQUE REQUIREMENTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.5 LUBRICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
Hydraulic Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
Lubrication Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.6 HYDRAULIC PRESSURE ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.7 CYLINDER SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.8 SERIAL NUMBER LOCATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
SECTION 2 - SERVICE PROCEDURES
2.1 MACHINE PREPARATION, INSPECTION, AND MAINTENANCE. . . . . . . . . . . . . . . . . . . . . . . 2-1
General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Preparation, Inspection, and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Pre-Start Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Pre-Delivery Inspection and Frequent Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Annual Machine Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Preventative Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.2 PREVENTIVE MAINTENANCE AND INSPECTION SCHEDULE. . . . . . . . . . . . . . . . . . . . . . . . 2-2
2.3 SERVICING AND MAINTENANCE GUIDELINES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Safety and Workmanship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Cleanliness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Components Removal and Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Component Disassembly and Reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Pressure-Fit Parts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Gaskets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Bolt Usage and Torque Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Hydraulic Lines and Electrical Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Hydraulic System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Lubrication and Servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Mast Chain Inspection Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Mast Cable Inspection Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

ii – JLG Lift – 3120775
TABLE OF CONTENTS
2.4 LUBRICATION INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Hydraulic System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Hydraulic Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Changing Hydraulic Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Lubrication Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
2.5 BATTERY CHARGER - ASSEMBLY AND DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Battery Charger Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Cover Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
Transformer Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
Printed Circuit Board Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
DC Circuit Breaker Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
AC Circuit Breaker and Voltage Selection Switch Replacement . . . . . . . . . . . . . . . . . . 2-10
Shunt Assembly, Varistor, and SCR Rectifier Replacement (See Illustration) . . . . . . . . 2-10
2.6 HYDRAULIC LIFT PUMP - SERVICING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
FENNER BRAND PUMP - Brush Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
Motor Cap/Motor Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
Motor Brush Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
Brush Housing Final Assembly Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12
MONARCH BRAND PUMP - Brush Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
Motor Assembly - Remove/Install - Reference Marks . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
Motor/Brush Cover - Remove/Install . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
Brush Carrier Assembly - Remove/Install . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14
Brush Assembly - Remove/Install . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14
TANK AND PUMP REMOVAL - (All Pumps) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15
Tank Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15
Filter Screen Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15
Pump Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15
Pressure Adjust Valve Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16
Pressure Check Valve Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16
2.7 HYDRAULIC LIFT CYLINDER - REMOVAL, INSPECTION AND REBUILD . . . . . . . . . . . . . . . 2-17
Cylinder Removal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17
Cylinder Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17
Lift Cylinder Component Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17
Cylinder Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-19
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-19
2.8 MAST ASSEMBLY AND DISASSEMBLY PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20
Mast Disassembly Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20
Platform Section Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20
Mast Section 4 Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21
Mast Section 3 Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21
Mast Section 2 Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21
Mast Section 1 Disassembly (All Masts) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21
2.9 MAST ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22
Mast Section 1 - Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22
Mast Section 2 - Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22
Mast Section 3 - Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26
Mast Section 4 - Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-27
Platform Mounting Section - Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28
2.10 MAST TO BASE FRAME INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28
2.11 MAST CHAINS/CABLES AND SEQUENCING CABLES ADJUSTMENT . . . . . . . . . . . . . . . . 2-29
Mast Chain/Cable Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29
Sequencing Cable Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-31
2.12 SEQUENCE CABLE REPLACEMENT KIT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-31
Remove Old Cable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-31
Replacement Cable Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-31
Clamp Installation (Drum/Socket Type) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-32

3120775 – JLG Lift – iii
TABLE OF CONTENTS
SECTION 3 - TROUBLESHOOTING
3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.2 Troubleshooting Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.3 Hydraulic Circuit Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.4 ELECTRICAL SYSTEM - MULTIMETER BASICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Backprobing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Min/Max . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Continuity Measurement Over Long Distances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Requirements: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
3.5 ELECTRICAL SWITCH TESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
Basic Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
Limit Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
Automatic Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
Switch Wiring - Low Side, High Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
LIST OF FIGURES
FIGURE NO. TITLE PAGE NO.
1-1. Hydraulic Pressure Setting - Adjustment Screw Located at Base of Pump Motor . . . . . . . . . 1-2
1-2. Torque Chart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
2-1. Lift Cylinder Internal Component Assembly Cross-Section. . . . . . . . . . . . . . . . . . . . . . . . . . 2-18
2-2. Mast Section - Assembly/Disassembly Reference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20
2-3. 15SP Mast Assembly Components. (5 Section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23
2-4. 12SP Mast Assembly Components. (4 Section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24
2-5. Mast Chain Routing Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25
2-6. Mast Chain/Cable/Sequence Cable Adjustment Components. (Typical) . . . . . . . . . . . . . . . 2-30
3-1. Voltage Measurement (DC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
3-2. Resistance Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
3-3. Continuity Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3-4. Current Measurement (DC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3-5. Hydraulic Schematic. (SP Series) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
3-6. Electrical Diagram (Standard) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8
3-7. Electrical Diagram (With Floor Brake/Gate Alarm Option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10
LIST OF TABLES
TABLE NO. TITLE PAGE NO.
1-1 Hydraulic Oil Operating Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1-2 Lubrication Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1-3 Cylinder Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1-4 Lubrication Intervals for Various Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
2-1 Inspection and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
2-2 Preventive Maintenance & Inspection Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2-3 Chain Stretch Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2-4 AM Series Mast Component Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20
3-1. DC Unit - Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

iv – JLG Lift – 3120775
TABLE OF CONTENTS
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JLG Vertical Mast 12SP, 15SP Service Repair Workshop Manual (P/N:3120775)
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Description
This comprehensive service repair workshop manual is designed for the JLG Vertical Mast 12SP and 15SP models. It is tailored for DIY repair enthusiasts and experienced mechanics alike, providing clear, easy-to-follow instructions and detailed illustrations to guide you through every repair and maintenance procedure.
- Step-by-step repair instructions with high-quality, detailed diagrams
- Comprehensive coverage of specifications, service procedures, troubleshooting, and more
- Printable pages for convenient reference during your repairs
This manual is an invaluable resource for those looking to maintain and repair their equipment effectively, ensuring your vehicle remains in optimal working condition.