11.1  Troubleshooting
11-11
11
Inspection, Maintenance, and Troubleshooting
A.C9
Encoder 
Communica-
tions Error
Occurred when the 
control power sup-
ply was turned ON 
or during operation. 
The encoder wiring and the contact are incorrect. Correct the encoder wiring.
Noise interference occurred due to incorrect 
encoder cable specifications.
Use tinned annealed copper twisted-pair or 
twisted-pair shielded wire with a core of at least 
0.12 mm
2
. 
Noise interference occurred because the wiring dis-
tance for the encoder cable is too long.
The wiring distance must be 20 m max.
The noise interference occurred on the signal line 
because the encoder cable is bent and the sheath is 
damaged.
Correct the encoder cable layout.
The encoder cable is bundled with a high-current 
line or near a high-current line.
Correct the encoder cable layout so that no surge 
is applied.
The FG electrical potential varies because of the 
influence from such machines on the servomotor 
side as welders.
Ground the machine separately from PG side FG.
Noise interference occurred on the signal line from 
the encoder.
Take a measure against noise for the encoder wir-
ing.
Excessive vibration and shocks were applied to the 
encoder.
Reduce the machine vibration or mount the ser-
vomotor securely.
An encoder fault occurred. Replace the servomotor.
A SERVOPACK board fault occurred. Replace the SERVOPACK.
A.CA
Encoder Param-
eter Error 
Occurred when the 
control power sup-
ply was turned ON. 
An encoder fault occurred. Replace the servomotor.
A SERVOPACK board fault occurred. Replace the SERVOPACK.
A.Cb
Encoder Echo-
back Error
Occurred when the 
control power sup-
ply was turned ON 
or during operation. 
The encoder wiring and contact are incorrect. Correct the encoder wiring.
Noise interference occurred due to incorrect 
encoder cable specifications.
Use tinned annealed copper twisted-pair or 
twisted-pair shielded wire with a core of at least 
0.12 mm
2
.
Noise interference occurred because the wiring dis-
tance for the encoder cable is too long.
The wiring distance must be 20 m max.
Noise interference occurred on the signal line, 
because the encoder cable is bent and the sheath is 
damaged.
Correct the encoder cable layout.
The encoder cable is bundled with a high-current 
line or near a high-current line.
Correct the encoder cable layout so that no surge 
is applied.
The FG electrical potential varies because of the 
influence from such machines on the servomotor 
side as welders.
Ground the machine separately from PG side FG.
Noise interference occurred on the signal line from 
the encoder.
Take measures against noise for the encoder wir-
ing.
Excessive vibration and shocks to the encoder was 
applied.
Reduce the machine vibration or mount the ser-
vomotor securely.
An encoder fault occurred. Replace the servomotor.
A SERVOPACK board fault occurred. Replace the SERVOPACK.
A.CC
Multiturn Limit 
Disagreement
Occurred when the 
control power sup-
ply was turned ON. 
The parameter settings for the SERVOPACK are 
incorrect.
Correct the setting of Pn205 (0 to 65535).
The multiturn limit value for the encoder is not set 
or was changed.
Execute Fn013 at the occurrence of alarm.
Occurred during 
normal operation. 
A SERVOPACK board fault occurred. Replace the SERVOPACK.
Table 11.3  Alarm Display and Troubleshooting (Cont’d)
Alarm 
Display
Alarm Name
Situation at Alarm 
Occurrence
Cause Corrective Actions