Code SV0437: Converter: input circuit overcurrent
Issue Description & Safety Warning
The Fanuc Alpha-i Servo Spindle Amplifier has triggered a critical Converter: input circuit overcurrent alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Amplifier LED display: 1 Also shown as: SV0437/SV0444 (15i), SV0437/SV0444 (30i/31i/32i), SV0437/SV0444 (0i-D) Cause: (1) Meaning The 200-V control power (CX1A) is not supplied. Alternatively, the 24-VDC power is short-circuited. (2) Cause and troubleshooting (a) Check whether the circuit breaker for the control power supply is off. When a lightning surge absorber is connected immediately following the circuit breaker, check whether the lightning surge absorber is short-circuited by lightning. If the lightning surge absorber is short-circuited, replace it. (b) Disconnect the cable from the connector CX1A and turn the control power on. If "-" is displayed, the 24-V power to a Servo Amplifier or Spindle Amplifier may be short-circuited. → Detect the amplifier which causes the power to be short-circuited by sequentially connecting the cable from the Power Supply and replace it. (c) Disconnect the cable from the connector CX4 and turn the control power on. If "-" is displayed, the external 24-V power may be connected to pin 3 of CX4 incorrectly. → Correct the connection.
Source: Fanuc αi Servo/Spindle Amplifier Maintenance Manual (B-65285EN/04) — Part II Troubleshooting
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Fanuc Alpha-i Servo Spindle Amplifier Alarms
Fanuc controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code SV0437 on the Alpha-i Servo Spindle Amplifier identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Fanuc's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 135 Fanuc Alpha-i Servo Spindle Amplifier codes.
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