Identify the Alarm Before Replacing Hardware
SV0436 and the reported 9055 indication describe different fault paths. SV0436 is a servo soft-thermal overload alarm identified as OVC. The supplied information associates 9055 with 7n55 and Alarm Code 55, but it does not define the display-format relationship between those identifiers. Confirm the complete displayed code before applying the Alarm Code 55 procedure.
| Indication | Confirmed meaning | Primary diagnostic path |
|---|---|---|
| SV0436 | Soft thermal overload, OVC | Motor vibration, power-lead wiring, overload parameters, and measured motor current |
| 9055 / 7n55 / Code 55 | Reported association; exact display mapping is not established by the evidence | Power-lead switching contactor, contact-feedback I/O and wiring, and ladder sequence |
Troubleshoot SV0436 Soft Thermal OVC
SV0436 indicates that the calculated overload condition has reached the soft-thermal OVC threshold. Diagnose excessive current and configuration errors before replacing the motor or amplifier.
- Check whether the motor vibrates. Vibration increases current and can produce the alarm.
- Verify that the motor power leads are connected correctly. An incorrect connection can cause abnormal motor current.
- Verify the overload-protection parameters against the standard values in FANUC AC SERVO MOTOR αis/αi series Parameter Manual B-65270EN.
- Attach the applicable check board to connector JX5 and measure actual servo-amplifier currents IR and IS while running the motor. The required check pin board differs from the board used for the α series.
- Compare IR and IS with the overload duty curve in FANUC AC SERVO MOTOR αis/αi series Descriptions B-65262EN. If current is high during acceleration or deceleration, investigate whether the time constant is too small.
| Function | FS15i | FS16i |
|---|---|---|
| OVC1 | 1877 | 2062 |
| OVC2 | 1878 | 2063 |
| OVCLMT | 1893 | 2065 |
| OVC21 | 1785 | 2162 |
| OVC22 | 1786 | 2163 |
| OVCLMT2 | 1787 | 2165 |
Troubleshoot the Reported 9055 or Alarm Code 55
Alarm Code 55 means that, during motor activation, the requested spindle or output switching state does not match the checked power-lead state. The request is represented by SPSL or RSL; feedback is represented by MCFN, MFNHG, RCH, or RCHHG.
- Inspect the magnetic contactor or switch unit used for power-lead switching. If it does not operate, check its power supply. Replace the contactor if it remains inoperative.
- Inspect the I/O unit and wiring that check the contactor state. Replace the defective I/O unit or wiring when a fault is confirmed.
- Review the ladder sequence. Modify it so switching does not occur during motor activation. Consult FANUC SERVO AMPLIFIER αi series Descriptions B-65282EN for the signal definitions.
Verify the Repair
For SV0436, run the motor through the operating condition that produced the alarm and confirm that vibration is absent, the power leads remain correct, and measured IR and IS comply with the applicable overload duty curve. For Alarm Code 55, monitor the switching request and contact-state feedback during motor activation; verify that the states agree and that the ladder does not initiate switching while activation is in progress.
FAQ
What causes FANUC SV0436?
SV0436 is a soft-thermal OVC overload alarm. Supported causes include motor vibration, incorrect motor power-lead connections, incorrect overload-protection parameters, excessive machine load, or excessive acceleration/deceleration current associated with a time constant that is too small.
Which FANUC parameters should I check for SV0436?
For FS15i, check 1877, 1878, 1893, 1785, 1786, and 1787. For FS16i, check 2062, 2063, 2065, 2162, 2163, and 2165 against B-65270EN standard values.
What should I check for FANUC Alarm Code 55?
Check the power-lead switching contactor and its supply, the contact-feedback I/O and wiring, and the ladder sequence. Confirm that SPSL or RSL agrees with MCFN, MFNHG, RCH, or RCHHG during motor activation.