Troubleshooting; Output Does Not Operate (Main Unit And Input/Output Extension Blocks); Dc Input Does Not Operate (Main Unit And Input/Output Extension Blocks) - Mitsubishi Electric MELSEC-F FX3G Series User Manual

FX Series Programmable Controllers
3G
User's Manual - Hardware Edition
14.7

Troubleshooting

→ For the procedures on operating peripheral devices, refer to the manuals for the peripheral devices.

14.7.1 Output does not operate (main unit and input/output extension blocks)

1. Output does not turn on.
Stop the PLC, and forcibly turn the inoperable output on then off with a peripheral device or the display
module to check its operation.
Check for troubles with external wiring.
• When the output operates
The output may be turned off unintentionally in the program. Reexamine the program.
(Duplicate coil or RST instructions)
• When the output does not operate
Check the configuration of the connected devices and the connection of the extension cables.
If the configuration of the external wiring and connected devices and the connection of the extension
cables are acceptable, the output circuit may be damaged.
Consult your local Mitsubishi Electric representative.
2. Output does not turn off.
Stop the PLC, and check that the output turns off.
Check for trouble with external wiring.
• When the output turns off
The output may be turned on unintentionally in the program.
Check that there are no duplicate coils in the program.
• When the output does not turn off
The output circuit may be damaged. Consult your local Mitsubishi Electric representative.
14.7.2 24V DC input does not operate (main unit and input/output extension blocks)
1. Input does not turn on.
Disconnect the external wiring and connect the S/S terminal and the 0V terminal or the 24V terminal.
Short-circuit the 0V terminal or 24V terminal not connected to the S/S terminal and the input terminal, then
check the input display LED or a peripheral device to confirm that the input turns on.
When input turns on
When input does not
turn on
2. Input does not turn off.
Check for leakage current from input devices.
If the leakage current is larger than 1.5mA, it is necessary to connect a bleeder resistance.
→ For the procedures on running and stopping the PLC, refer to Section 14.2.
→ For the procedures on running and stopping the PLC, refer to Section 14.2.
Check that the input device does not have a built-in diode or parallel resistance.
If so, refer to Subsection 10.2.2.
Measure the voltage between the 0V terminal or 24V terminal not connected to the S/S terminal and the input
terminal with a tester to confirm that the voltage is 24V DC.
• Check the configuration of the external wiring and connected devices and the connection of the extension
cables.
14 Test Operation, Adjustment, Maintenance and Troubleshooting
Measures
→ For details on the measures, refer to Subsection 10.2.2.
14.7 Troubleshooting
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