JLG T350 Troubleshooting Manual page 119

Open-Circuit Pump Motor
This issue will prevent the Pump Motor from operating. 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 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 ter-
minals. After examination, re-connect the Pump Motor Positive Terminal and the Main Battery Disconnect.
Short-Circuit between Pump Motor Positive and Negative Terminals
This issue will prevent the Pump Motor from operating. 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 independently. 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 com-
partment for a short-circuit. 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 amme-
ter will read approximately 150A.
Power Module Electrical Evaluation
Several basic electrical tests can be performed on the Power Module. Failure of one of these evaluations is significant 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.
Make all measurements with a voltmeter set to resistance scale (Ohms). Disconnect the Main Battery Disconnect and all
cables from 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).
1. Resistance >100kOhms all Terminals to Housing. Ensure that there is an open-circuit between all terminals of the
Power Module and the module's aluminum 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.
2. 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 current measurement shunt for the Armature portion of Traction. Place the Red
meter lead on B+, and the Black meter lead on M1.
3. Resistance >1MegaOhms 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.
4. Resistance >1MegaOhms 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.
5. 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-impedance 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.
6. Resistance >1kOhms between M2 and B-. Ensure that there is an open-circuit between the M2 and B- Terminals. Inter-
nally, 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 M2. Note that a measurement of increasing
resistance (capacitor charge) is normal, but a persistently low impedance is not.
7. Resistance 120 Ohms between Pins 10 & 11. Ensure that the resistor that terminates the CAN bus 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.
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SECTION 3 - COMPONENT CHECKS
T350 T500J 3-119