SECTION 3 - CHASSIS & SCISSOR ARMS
31215074
3-3
1. Open-Circuit between +B Terminal and Pump
Motor Positive 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 DIAGNOSTICS -
PUMP, the JLG Analyzer will show PUMP PWM
100% and PUMP CUR 0.0A when Lift Up is oper
-
ated from Ground Mode.
As shown in the diagram, the voltage measured
between the Pump Motor Positive Terminal and
Ground Reference should be 24V. If it is not, exam
-
ine the cable between the terminal and the Power
Module compartment. Inspect crimps for corro
-
sion and ensure that bolted connections are tight.
Ensure that the cable is not crushed where it
passes between the frame side sheets and the cyl
-
inder assembly.
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 DIAGNOSTICS -
PUMP, the JLG Analyzer will show PUMP PWM
100% and PUMP CUR 0.0A when Lift Up is oper
-
ated 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). Inspect crimps for cor
-
rosion and ensure that bolted connections are
tight. Ensure that the cable is not crushed where it
passes between the frame side sheets and the cyl
-
inder 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 DIAGNOSTICS -
PUMP, the JLG Analyzer will show PUMP PWM
100% and PUMP CUR 0.0A when Lift Up is oper
-
ated from Ground Mode.
Pull the Main Battery Disconnect to completely
de-energize the Control System. Next, detach the
cable from Pump Motor Positive Terminal. Using a
voltmeter set for resistance measurement (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 terminals. After examination,
re-connect the Pump Motor Positive Terminal and
the Main Battery Disconnect.
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 DIAGNOSTICS -
PUMP, the JLG Analyzer will show an erratic read
-
ing for PUMP PWM % and PUMP CUR will hover
around 150A when Lift Up is operated from
Ground Mode.
Pull the Main Battery Disconnect to completely
de-energize the Control System. Next, detach both
Pump Motor Terminals and insulate them inde
-
pendently. Re-connect the Main Battery Discon
-
nect and re-try Lift Up. If the same symptoms
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 the symptoms change, sus
-
pect 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 approx
-
imately 150A.
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