SECTION 4 - BASIC HYDRAULIC INFORMATION & SCHEMATICS
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4-3
2. Open-Circuit between Pump Motor Negative
Terminal and P Terminal
This issue will allow the vehicle to drive, but Lift
Up and Steer Functionality will be lost and the
Pump Motor will not operate. Under DIAGNOS-
TICS - PUMP, the JLG Analyzer will show PUMP
PWM 100% and PUMP CUR 0.0A when Lift Up is
operated from Ground Mode.
After ensuring there is not an Open-Circuit
between the +B Terminal and Pump Motor Posi-
tive Terminal, check that the voltage measured
between the Pump Motor Negative Terminal
and Ground Reference is 24V. If not, examine the
issues within Open-Circuit Pump Motor. This
voltage should ramp to approximately 0V when
Lift Up is operated from Ground Mode. If not,
examine the cable between the terminal and the
Power Module compartment (P Terminal). Exam-
ine crimps for corrosion and ensure that bolted
connections are tight. Ensure that the cable is
not crushed where it passes between the frame
side sheets and the cylinder assembly.
3. Open-Circuit Pump Motor
This issue will allow the vehicle to drive, but Lift
Up and Steer Functionality will be lost and the
Pump Motor will not operate. Under DIAGNOS-
TICS - PUMP, the JLG Analyzer will show PUMP
PWM 100% and PUMP CUR 0.0A when Lift Up is
operated from Ground Mode.
Disconnect main power at the batteries to com-
pletely de-energize the Control System. Next,
detach the cable from Pump Motor Positive Ter-
minal. Using a voltmeter set for resistance mea-
surement (Ohms), ensure that the resistance
between the Pump Motor Positive and Negative
Terminals is less than 2 Ohms. If not, examine the
pump motor for worn brushes or broken termi-
nals. After examination, re-connect the Pump
Motor Positive Terminal and main power at the
batteries.
4. Short-Circuit between Pump Motor Positive
and Negative Terminals
This issue will allow the vehicle to drive, but Lift
Up and Steer Functionality will be lost and the
Pump Motor will not operate. Under DIAGNOS-
TICS - PUMP, the JLG Analyzer will show an
erratic reading for PUMP PWM % and PUMP CUR
will hover around 150A when Lift Up is operated
from Ground Mode.
Disconnect main power at the batteries to com-
pletely de-energize the Control System. Next,
detach both Pump Motor Terminals and insulate
them independently. Re-connect main power at
the batteries and re-try Lift Up. If the same symp-
toms persist (erratic PUMP PWM%, PUMP CUR
around 150A), examine the cabling between the
Pump Motor and Power Module compartment
for a short-circuit (most likely near area where
cylinder retracts between frame side sheets or
near pot-hole mechanism, if equipped). If the
symptoms change, suspect a short-circuited (or
mechanically frozen) pump motor.
A clamp-on ammeter (set for 200A DC) can be
placed on either Pump Motor Cable for verifica-
tion. During Lift Up, the ammeter will read
approximately 150A.
-B
P
+B
Series DC
Pump Motor
24V
Line Contactor
Power Module
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