JLG 3248RS/10RS Service Manual - Manual (Page 47)

SECTION 3 - CHASSIS & SCISSOR ARMS
3121273 – JLG Lift – 3-15
Common Traction System Difficulties
1. Ground Module Interlocks
There are a variety of interlocks that prevent Drive
due to system events. Before investigating Traction
System issues, examine the JLG Analyzer's HELP
Menu while attempting to Drive from Platform Mode.
Refer to the Section 5 for explanation of the JLG
Analyzer Help Messages.
2. Power Module Diagnostic Issues
The Power Module executes a self-test during every
power-up to ensure proper functionality. If a Diag-
nostic Issue is detected, the Power Module will not
energize the Main Power Contactor. Instead, it will
flash the Green LED, please refer to ZAPI Power
Module Electrical Evaluation - page 3-18.
3. Open-Circuit Motor Armature
This issue will allow the vehicle to drive, but one
motor will handle the entire traction load. Motor
overheating and excessive tire wear will result, along
with a lack of traction control.
This situation can be detected by elevating the vehi-
cle's front wheels and engaging drive (platform
stowed). Under DIAGNOSTICS - TRACTION, the
JLG Analyzer's ARM CUR display (Armature Current
Reading) should be less than 50A. One wheel will
rotate at full speed, while the other will not rotate at
all. The Power Module's self-diagnostics cannot
detect this fault unless both armatures are open-cir-
cuit.
To find the source of the difficulty, disconnect main
power at the batteries and investigate the wiring
pathways from the Power Controller's M1 and M2
terminals to the armature on the motor that does not
rotate. Investigate for issues like improper crimps,
loose terminals, and corrosion.
4. Short-Circuit Motor Armature
This issue will allow the vehicle to drive very slowly
or not at all. Rapid motor overheating (one motor)
will result.
This situation can be detected by elevating the vehi-
cle's front wheels and engaging drive (platform
stowed). Under DIAGNOSTICS - TRACTION, the
JLG Analyzer's ARM CUR display (Armature Current
Reading) will hover around 350A. The FLD CUR dis-
play (Field Current Reading) will hover around 40A.
Neither wheel will rotate at normal speed, but it will
be possible to rotate the drive wheel by hand. The
Power Module's self-diagnostics cannot detect this
fault since the situation appears identical to climbing
a steep grade.
To find the source of the difficulty, disconnect main
power at the batteries and disconnect the Armature
Wiring (heavy red and black conductors) from the
suspected drive motor leading to the Power Mod-
ule's M1 and M2 Terminals. Re-test the traction func-
tion. If the remaining drive motor is able to reach full
speed (and Armature Current is less than 50A), the
drive motor that has been disconnected is fault.
Investigate for crushed and burned cables. Check if
the drive motor smells burned.
5. Open-Circuit Motor Field
This issue will allow the vehicle to drive very slowly
or not at all. Rapid motor overheating (both motors)
will result.
This situation can be detected by elevating the vehi-
cle's front wheels and engaging drive (platform
stowed). Under DIAGNOSTICS - TRACTION, the
JLG Analyzer's ARM CUR display (Armature Current
Reading) will hover around 350A. The FLD CUR dis-
play (Field Current Reading) will be erratic or low
(less than 10A). Neither wheel will rotate at normal
speed, but it will be possible to rotate the drive
wheel by hand.
To find the source of the difficulty, pull the Main Bat-
tery Disconnect and disconnect the Field Wiring
(two blue wires leading to F1 and F2 Terminals) from
the Power Module. Using a voltmeter set for resis-
tance scale (Ohms), investigate if there is a short-cir-
cuit (less than 5 Ohms) between the two blue wires
(this is normal). If not, investigate for improper
crimps, burned cables, damaged cables, or dam-
aged field windings.
6. Short-Circuit Brake Release
This issue will not allow the vehicle to drive. Rapid
motor overheating (both motors) will result. Contin-
ued attempts to drive the vehicle may result in arma-
ture damage.
This situation can be detected by elevating the vehi-
cle's front wheels and engaging drive (platform
stowed). Under DIAGNOSTICS - TRACTION, the
JLG Analyzer's ARM CUR display (Armature Current
Reading) will hover around 350A. The FLD CUR dis-
play (Field Current Reading) will hover around 40A.
Neither wheel will rotate, and it will be impossible to
rotate either drive wheel by hand. The Ground Mod-
ule cannot detect this fault during power-up or self-
test since energizing the brakes could pose a haz-
ard. However, it may detect this issue during Drive
(investigate using JLG Analyzer).