NAiS FP Series User Manual page 244

FPΣ
12.2.2 If the ERROR/ALARM LED Lights
Condition: The system watchdog timer has been activated and the operation of
PLC has been stopped.
Procedure 1
Set the mode selector of PLC from RUN to PROG. mode and turn the power off and then
on.
- If the ERROR/ALARM LED is turned on again, there is probably an abnormality in
the FPΣ control unit. Please contact your dealer.
- If the ERROR/ALARM LED is flashed, go to page 12 - 5.
Procedure 2
Set the mode selector from PROG. to RUN mode.
- If the ERROR/ALARM LED is turned on, the program execution time is too long.
Check the program, referring the following:
Check if instructions such as "Jump" or "LOOP" are programmed in such a way
that a scan can never finish.
Check that interrupt instructions are executed in succession.
12.2.3 If None of the LEDs Light
Procedure 1
Check wiring of power supply.
Procedure 2
Check if the power supplied to the FPΣ control unit is in the range of the rating.
- Be sure to check the fluctuation in the power supply.
Procedure 3
Disconnect the power supply wiring to the other devices if the power supplied to the FPΣ
control unit is shared with them.
- If the LED on the control unit turn on at this moment, increase the capacity of the
power supply or prepare another power supply for other devices.
12.2 Troubleshooting
12 - 7