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The JLG 40E and Its Electric Drive System
The JLG 40E is an electric boom lift designed for indoor and outdoor use where zero emissions and quiet operation are essential. Manufactured by JLG Industries, a company founded in 1969 and now part of Oshkosh Corporation, the 40E features a DC electric motor system controlled by a SEVCON motor controller. This controller regulates power delivery, acceleration, and braking through a series of terminals and logic inputs.
The SEVCON controller used in the 40E (part number 7013310) is a programmable unit that interfaces with the lift’s control system, battery pack, and drive motors. Terminal assignments vary slightly by model and configuration, but terminal 3 is typically associated with a power input or logic signal required for controller activation.
Terminology Notes
While troubleshooting an intermittent electrical fault, a technician inadvertently disconnected a red wire leading to terminal 3. The schematic provided by JLG did not show a wire at that terminal, leading to confusion. Two local technicians attempted to reconnect the wire to various red wires in the harness, but the lift remained unresponsive.
Key observations:
One technician shared that a similar issue on a Genie lift was resolved by tracing the red wire to a key switch relay. Another recalled that SEVCON controllers often require a specific logic voltage to boot up, and missing this signal causes the lift to appear dead.
A mechanic in Oregon emphasized the importance of using manufacturer-specific wiring diagrams rather than generic schematics. He noted that aftermarket manuals often omit controller internals, leading to misdiagnosis.
Preventive Measures and Long-Term Solutions
A disconnected red wire at terminal 3 on a JLG 40E motor controller likely relates to logic power or enable signal. Without proper voltage at this terminal, the controller will not activate, leaving the lift inoperable. Random reconnection attempts risk damaging the unit. By tracing the wire, consulting OEM documentation, and testing voltage under controlled conditions, technicians can restore functionality without costly replacements. In electric lifts, precision matters—especially when the schematic goes silent.
The JLG 40E is an electric boom lift designed for indoor and outdoor use where zero emissions and quiet operation are essential. Manufactured by JLG Industries, a company founded in 1969 and now part of Oshkosh Corporation, the 40E features a DC electric motor system controlled by a SEVCON motor controller. This controller regulates power delivery, acceleration, and braking through a series of terminals and logic inputs.
The SEVCON controller used in the 40E (part number 7013310) is a programmable unit that interfaces with the lift’s control system, battery pack, and drive motors. Terminal assignments vary slightly by model and configuration, but terminal 3 is typically associated with a power input or logic signal required for controller activation.
Terminology Notes
- SEVCON Controller: A brand of motor controller used in electric vehicles and lifts, known for programmable logic and compact design.
- Terminal 3: A numbered connection point on the controller; often used for power or enable signals.
- Logic Power: Low-voltage input that activates the controller’s internal circuits.
- Intermittent Fault: A sporadic electrical issue that appears and disappears unpredictably, often due to loose wires or corroded terminals.
While troubleshooting an intermittent electrical fault, a technician inadvertently disconnected a red wire leading to terminal 3. The schematic provided by JLG did not show a wire at that terminal, leading to confusion. Two local technicians attempted to reconnect the wire to various red wires in the harness, but the lift remained unresponsive.
Key observations:
- The red wire was previously connected to terminal 3 on the SEVCON controller.
- The wire’s origin was unclear, and the schematic lacked detail.
- The lift exhibited intermittent electrical faults prior to disconnection.
- Reconnecting the wire randomly did not restore function.
- Logic Power Input: Supplies low-voltage power (typically 12V or 24V) to activate the controller.
- Key Switch Signal: Receives voltage when the ignition or enable switch is turned on.
- Battery Positive Feed: May be tied to the main battery pack through a fuse or relay.
- Enable Line: A signal that tells the controller to begin operation when conditions are met.
- Trace the Red Wire: Use a multimeter to check continuity from the wire to other components. Look for voltage when the key switch is on.
- Check Controller Documentation: SEVCON controllers often have detailed pinout charts available from the manufacturer or authorized dealers.
- Inspect Nearby Terminals: Look for signs of previous connections, wear, or solder residue.
- Test for Voltage at Terminal 3: With the key on, measure voltage at terminal 3. If absent, the controller may not activate.
- Avoid Random Reconnection: Connecting power to the wrong terminal can damage the controller.
One technician shared that a similar issue on a Genie lift was resolved by tracing the red wire to a key switch relay. Another recalled that SEVCON controllers often require a specific logic voltage to boot up, and missing this signal causes the lift to appear dead.
A mechanic in Oregon emphasized the importance of using manufacturer-specific wiring diagrams rather than generic schematics. He noted that aftermarket manuals often omit controller internals, leading to misdiagnosis.
Preventive Measures and Long-Term Solutions
- Label Wires During Disassembly: Use numbered tags or colored tape to avoid confusion.
- Photograph Wiring Before Repairs: Visual records help restore original connections.
- Request OEM Schematics: Contact JLG or SEVCON directly for controller-specific diagrams.
- Install Diagnostic LED Indicators: Some controllers support external LEDs to show status codes.
- Consider Controller Replacement Only After Exhaustive Testing: New SEVCON units can cost over $1,000 and require programming.
A disconnected red wire at terminal 3 on a JLG 40E motor controller likely relates to logic power or enable signal. Without proper voltage at this terminal, the controller will not activate, leaving the lift inoperable. Random reconnection attempts risk damaging the unit. By tracing the wire, consulting OEM documentation, and testing voltage under controlled conditions, technicians can restore functionality without costly replacements. In electric lifts, precision matters—especially when the schematic goes silent.
