JLG 1230ES Service Manual - Manual (Page 65)

SECTION 4 - BASE COMPONENTS
3121222 – JLG Lift – 4-29
4.9 HYDRAULIC PUMP/MOTOR/VALVE ASSEMBLY - SERVICE PROCEDURE
Refer to Section 3.6, PUMP/LIFT/MAST - Theory of Opera-
tion for more detailed information on Pump/Motor/Valve
System.
Common Difficulties
The following difficulties can be examined using the JLG
Analyzer, a voltmeter, and simple hand tools. Unless oth-
erwise noted, the Control System shall be energized in
Ground Mode during testing. For a convenient Ground
Reference, place the black meter lead on the negative
post of the left battery in the left-side battery compartment.
The vehicle should be placed on a firm, level surface for
all analysis.
1. Ground Module Interlocks
There are a variety of interlocks that prevent Lift Up
due to system events (Tilted, Elevation Angle Sensor
Not Calibrated, etc). Before investigating Pump Sys-
tem issues, examine the JLG Analyzer's HELP Menu
while attempting to Lift Up from Ground Mode.
Refer to Section 5 for explanations of the 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 Line Contactor. Instead, it will flash the
Green LED. Since these issues may impact both the
Traction and Pump Systems, please refer to the sec-
tion for Power Module Diagnostics.
3. 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 operated 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 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.
4. Open-Circuit between Pump Motor Negative Ter-
minal 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 operated from
Ground Mode.
After ensuring there is not an Open-Circuit between
the +B Terminal and Pump Motor Positive 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 approxi-
mately 0V when Lift Up is operated from Ground
Mode. If not, examine the cable between the termi-
nal and the Power Module compartment (P Termi-
nal). Inspect 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.
5. 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 operated 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 voltme-
ter 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 bro-
ken terminals. After examination, re-connect the
Pump Motor Positive Terminal and the Main Battery
Disconnect.
6. 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 reading
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 indepen-
dently. Re-connect the Main Battery Disconnect 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, 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 verification.
During Lift Up, the ammeter will read approximately
150A.