Power Module Electrical Evaluation - JLG 1930ES Service Maintenance Manual

investigate using resistance measurement (refer to
Drive Motor Electrical Evaluation). Suspect dam-
aged cabling, burned cabling, or faulty brake
release solenoids. Trace the brake release cabling
from the Power Module Compartment to the
Ground Module Connector J1-24.
3. Open-Circuit Brake Release
This issue will not allow the vehicle to drive. Rapid
motor overheating (both motors) will result. Con-
tinued attempts to drive the vehicle may result in
armature damage.
This situation can be detected by elevating the
vehicle's front wheels and engaging drive (plat-
form stowed). Under DIAGNOSTICS - TRACTION,
the JLG Analyzer's ARM CUR display (Armature
Current Reading) will exceed 120A. The FLD CUR
display (Field Current Reading) will hover around
40A. It is possible that one wheel may rotate, or
neither may rotate (depending on the location of
the open-circuit). Listen for the brake release sole-
noid when activating drive. The Ground Module
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).
If one wheel rotates, the open-circuit is located in
the wiring for that specific drive motor (Power
Module compartment or Drive Motor Cable).
Investigate for improper crimps, unlatched con-
nectors, damaged cables, or open brake release
solenoids (refer to Drive Motor Electrical Evalua-
tion).
If neither wheel rotates, the open-circuit is located
in the wiring between the Power Module compart-
ment and Ground Module. Using a voltmeter, mea-
sure the brake release voltage on either brake
connector in the Power Module compartment dur-
ing drive (should be approximately 24V). Investi-
gate for improper crimps, unlatched connectors,
damaged harnessing, or a faulty Ground Module.
As an alternative, insert a short piece of wire with a
Deutsch Female Crimp directly into Ground Mod-
ule's J1-24 and measure voltage as a diagnostic
measure (eject vehicle harness from that pin).

Power Module Electrical Evaluation

Several basic electrical tests can be performed on the
Power Module. Failure of one of these evaluations is sig-
nificant and may indicate that the device is physically
damaged. If a Power Module is suspected to be faulty,
thoroughly examine the rest of the system for possible
damage.
Refer to Figure 7-2., Resistance Measurement. Discon-
nect the Main Battery Disconnect and all cables from
3121656
SECTION 3 - CHASSIS & SCISSOR ARMS
the Power Module during this analysis. Wait 60 seconds
after power is disconnected to allow internal charge to
dissipate (risk of hazard, improper readings otherwise).
• Resistance >100kOhms all Terminals to Housing.
Ensure that there is an open-circuit between all ter-
minals of the Power Module and the module's alumi-
num housing. The device is fully potted and all
electronics are insulted from the housing. Place the
Black meter lead on the housing and use the Red
meter lead to probe all terminals.
• Resistance < 2 Ohms between +B and M1. Ensure
that there is a short-circuit between the +B and M1
Terminals. Internally, there is a low-impedance cur-
rent measurement shunt for the Armature portion of
Traction. Place the Red meter lead on +B, and the
Black meter lead on M1.
• Resistance >1 MegaOhms between F1 and -B; F2
and -B. Ensure that there is an open-circuit between
the two Field Terminals (F1 & F2) and -B. Internally,
there are MOSFET transistors between these termi-
nals that should be high-impedance when the mod-
ule is un-powered. Place the Black meter lead on -B
and the Red meter lead on F1 / F1.
• Resistance >1 MegaOhms between F1 and +B; F2
and +B. Ensure that there is an open-circuit
between the two Field Terminals (F1 & F2) and +B.
Internally, there are MOSFET transistors between
these terminals that should be high-impedance
when the module is un-powered. Place the Black
meter lead on +B and the Red meter lead on F1 / F1.
• Resistance >100kOhms between P and -B. Ensure
that there is an open-circuit between the P and the -
B Terminals. Internally, there are MOSFET transistors
between these terminals that should be high-imped-
ance when the module is un-powered. Place the
Black meter lead on -B, and the Red meter lead on P.
Note that a measurement of increasing resistance
(capacitor charge) is normal, but a persistently low
impedance is not.
• Resistance >1kOhms between M2 and -B. Ensure
that there is an open-circuit between the M2 and -B
Terminals. Internally, there are MOSFET transistors
between these terminals that should be high-imped-
ance when the module is un-powered. Place the
Black meter lead on -B, and the Red meter lead on
M2. Note that a measurement of increasing resis-
tance (capacitor charge) is normal, but a persistently
low impedance is not.
• Resistance 120 Ohms between Pins 10 & 11.
Ensure that the resistor that terminates the CANbus
is within tolerance between pins 10 and 11 on the 12
position Mini-Fit Jr (Connector "B"). Place the Red
meter lead on pin 10, and the Black meter lead on pin
11. The resistance should measure between 110 - 130
Ohms.
– JLG Lift – 3-3