Mitsubishi MELSEC iQ-F FX5UC, User Manual

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9 TROUBLESHOOTING
9.7 Troubleshooting for Each Symptom
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9
9.7
Troubleshooting for Each Symptom
When the CPU module does not operate properly, check an appropriate item from the following and perform troubleshooting.
I/O operation (CPU module, I/O module)
Output does not turn on
Output does not turn off
Input does not turn on
Input does not turn off
Item to check Action
Check for errors with external wiring. Connect the external wiring properly.
Stop the PLC, and forcibly turn on or off the inoperable output with a
peripheral device or an engineering tool. ■ When the output operates
The output may be turned off unintentionally in the program. Review user
program (Duplicate coils 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, there may be a hardware
issue. Consult your local Mitsubishi Electric representative.
Item to check Action
Check for errors with external wiring. Connect the external wiring properly.
Stop the PLC and check that the output turns off. ■ When the output turns off
The output may be turned on unintentionally in the program. Review user
program (Duplicate coils or RST instructions).
■ When the output does not turn off
There may be a hardware issue. Consult your local Mitsubishi Electric
representative.
Item to check Action
■
FX5UC-  MT/D
Remove the external wiring, and short-circuit the COM terminal and the input
terminal. Check that the input turns on with LEDs and peripheral devices.
■
When the input turns on
Check that the input device does not have a built-in diode or parallel
resistance.
If so, refer to

Page 86 Precautions for connecting input devices.
■
When the input does not turn on
Remove the external wiring, and measure the voltage between the COM
terminal and the input terminal with a tester to check that the voltage is 24 V
DC.
When the input voltage is lower than 20.4 V DC, check that the PLC power
supply voltage is "24 V DC +20%, -15%".
Check the configuration of the external wiring and connected devices and the
connection of the extension cables.
■ FX5UC-  MT/DSS
Remove the external wiring, and apply 24 V DC voltage between the COM 
terminal and the input terminal. Check that the input turns on with LEDs and
peripheral devices.
■ When the input turns on
Check that the input device does not have a built-in diode or parallel
resistance.
If so, refer to
 Page 86 Precautions for connecting input devices.
■ When the input does not turn on
Check that the voltage between the COM  terminal and the input terminal is
approx. 24 V DC with a tester.
When the input voltage is lower than 20.4 V DC, check that the external power
supply voltage is "24 V DC +20%, -15%".
Check the configuration of the external wiring and connected devices and the
connection of the extension cables.
Item to check Action
Check that there is no leakage current from input devices. If the leakage current is 1.5 mA or more, connect a bleeder resistance.
(

Page 86 Precautions for connecting input devices)