Troubleshooting With Leds; Pow Led [On/Flashing/Off]; Err Led [On/Flashing/Off] - Mitsubishi Electric MELSEQ FX3S Series User Manual

FX Series Programmable Controllers
3S
User's Manual - Hardware Edition
14.5

Troubleshooting with LEDs

When trouble occurs, check the LEDs on the PLC to identify the problem with the PLC.

14.5.1 POW LED [on/flashing/off]

LED
Status
Power of the specified voltage is being correctly
On
supplied to the power supply terminal.
One of the following problems may have occurred.
• Power of the specified voltage and current is not
Flashing being supplied to the power supply terminal.
• External wiring is incorrect.
• Internal error of PLC
One of the following problems may have occurred.
• The power supply is off.
• External wiring is incorrect.
Off
• Power of the specified voltage is not being
supplied to the power supply terminal.
• The power cable is broken.

14.5.2 ERR LED [on/flashing/off]

LED
Status
A watchdog timer error may have occurred,
On or the hardware of the PLC may be
damaged.
One of the following errors has occurred in
the PLC.
Flashing • Parameter error
• Syntax error
• Ladder error
Off No errors that stop the PLC have occurred.
132
14 Test Operation, Adjustment, Maintenance and Troubleshooting
PLC Status
PLC Status
1) Stop the PLC, and re-apply power.
2) Remove the PLC and supply power to it from another power supply on a
3) If the ERR LED does not go off even after the measures stated in (1) and
Perform PLC diagnosis and program check with the programming tool.
For the remedies, refer to Section 14.6.
If the operations of the PLC are abnormal, perform PLC diagnosis and
program check with the programming tool.
A Serial communication error or Operation error may have occurred.
The power supply is normal.
• Check the supply voltage.
• After disconnecting the cables other than the power cable, re-
apply power to the PLC, and check for changes in the state. If the
problem persists, consult
representative.
• If the power is not off, check the power supply and the power
supply route.
• If power is being supplied correctly, consult your local Mitsubishi
Electric representative.
• After disconnecting the cables other than the power cable, re-
apply power to the PLC, and check for changes in the state. If the
problem persists, consult
representative.
If ERR LED goes off, a watchdog timer error may have occurred. Take
any of the following measures.
- Review the program.
The maximum value (D8012) of the scan time should not exceed the
setting (D8000) of the watchdog timer.
- Check that the input used for input interruption or pulse catch is not
being abnormally turned on and off in one scan.
- Check that the frequency of the pulse (duty of 50%) input to the high-
speed counter does not exceed the specified range.
- Add the WDT instructions.
Add some WDT instructions to the program, and reset the watchdog
timer several times in one scan.
- Change the setting of the watchdog timer.
Change the watchdog timer setting (D8000) in the program so that the
setting is larger than the maximum value of the scan time (D8012).
desk.
If the ERR LED goes off, noise may have affected the PLC.
Take the following measures.
- Check the ground wiring, and reexamine the wiring route and
installation location.
- Fit a noise filter onto the power supply line.
(2) are taken, consult your local Mitsubishi Electric representative.
14.5 Troubleshooting with LEDs
Remedies
your local Mitsubishi
your local Mitsubishi
Action
Electric
Electric