Omron SYSMAC CS Series Operation Manual page 613

Troubleshooting Racks and Units
Symptom
Specific bit does not turn
OFF.
Input irregularly turns
ON/OFF.
Error occurs in units of
8 points or 16 points, i.e., for
the same common.
Input indicator is not lit in nor-
mal operation.
Output Units
Symptom
Not all outputs turn ON
Not all outputs turn OFF
Output of a specific bit num-
ber does not turn ON or indi-
cator is not lit.
Output of a specific bit num-
ber does not turn ON (indica-
tor lit).
Output of a specific bit num-
ber does not turn OFF (indi-
cator is not lit).
Cause
(1) Input circuit is faulty.
(2) Input bit number is used for output
instruction.
(1) External input voltage is low or unstable. Adjust external input voltage to within rated
(2) Malfunction due to noise.
(3) Terminal block screws are loose.
(4) Faulty terminal block connector contact. Replace terminal block connector.
(1) Common terminal screws are loose.
(2) Faulty terminal block connector contact. Replace terminal block connector.
(3) Faulty data bus
(4) Faulty CPU
Faulty indicator or indicator circuit.
Cause
(1) Load is not supplied with power.
(2) Load voltage is low.
(3) Terminal block screws are loose.
(4) Faulty terminal block connector contact. Replace terminal block connector.
(5) An overcurrent (possibly caused by a
short at the load) resulted in a blown
fuse in the Output Unit. (Some Output
Units provide an indicator for blown
fuses.)
(6) Faulty I/O bus connector contact.
(7) Output circuit is faulty.
(8) If the INH indicator is lit, the Output OFF
Bit (A50015) is ON.
Output circuit is faulty.
(1) Output ON time too short because of a
mistake in programming.
(2) Bit status controlled by multiple instruc-
tions.
(3) Faulty output circuit.
(1) Faulty output device.
(2) Break in output wiring.
(3) Loose terminal block screws.
(4) Faulty terminal block connector faulty.
(5) Faulty output bit.
(6) Faulty output circuit.
(1) Faulty output bit.
(2) Bit does not turn OFF due to leakage
current or residual voltage.
Remedy
Replace Unit.
Correct program.
range.
Take protective measures against noise,
such as:
(1) Increase input response time (PLC
Setup)
(2) Install surge suppressor.
(3) Install insulation transformer.
(4) Install shielded cables between the Input
Unit and the loads.
Tighten screws.
Tighten screws.
Replace Unit.
Replace CPU.
Replace Unit.
Remedy
Supply power
Adjust voltage to within rated range.
Tighten screws.
Replace fuse or Unit.
Replace Unit.
Replace Unit.
Turn A50015 OFF.
Replace Unit.
Correct program to increase the time that
the output is ON.
Correct program so that each output bit is
controlled by only one instruction.
Replace Unit.
Replace output device.
Check output wiring.
Tighten screws.
Replace terminal block connector.
Replace relay or Unit.
Replace Unit.
Replace relay or Unit.
Replace external load or add dummy resis-
tor.
Section 11-3
575