JLG ES series scissor lifts (1930ES, 2030ES, 2630ES, 2646ES, 3246ES)
JLG error code 311 — OPEN CIRCUIT LINE CONTACTOR
Message on the display: OPEN CIRCUIT LINE CONTACTOR
Code 311 occurs in machines: JLG ES series, 1932RS, 6RS, 3248RS, 10RS, 4045R, R4045.
blocking fault
The power modules line contactor did not close when energized. Drive, steer and lift up prevented.
Description from the JLG service manual, in the original wording.
Possible causes
The manual does not list the causes for this code: the service technician establishes them during diagnosis of the machine.
Checks from the manual
- Check contactor main contact wiring to battery (+) terminal and power controller terminal B+.
- Contactor solenoid resistance should measure about 52 Ohms.
- Check contactor solenoid wiring to power module 12 position connector terminal 8 and ground board terminal J1-19.
- Check that power module 12 position connector terminal 8 goes from 24V to near 0V while contactor should be closing. If this happens replace contactor.
- Replace the line contactor.
What service does
A qualified service technician reads the code with the manufacturer's diagnostic tools, finds the cause, clears the code and carries out a function test.
Source: JLG Service and Maintenance Manual, ES series (Diagnostic Trouble Codes section).
The descriptions are quoted from the manufacturer's service documentation and are for guidance only. Clearing codes, calibrations and repairs are carried out by a qualified service technician according to the manual for the specific serial number. A machine with an active blocking code must not be used until the cause has been removed.
Does code 311 not go away?
RK Rental services JLG lifts at our workshop or on site at the customer's premises (construction site, factory, warehouse). We read the code, remove the cause and select the parts by serial number.