SP9003 (Alarm 03) DC Fuse Open / Input Fuse fault in Fanuc drive

SP9003 (Alarm 03) DC Fuse Open / Input Fuse fault in Fanuc drive

Description

SP9003 appears on the Spindle Amplifier. It indicates that one of the internal fuses protecting the DC Link or the Control Power circuit has blown. This is a hardware failure alarm. On modern drives, it detects the voltage drop across the fuse. On older drives, there is a small "flag fuse" that physically pops up.

Cause

• DC Link Short: The power transistors (IGBTs) have shorted, causing a massive current spike that blew the safety fuse immediately.
• Control Circuit Short: A short in the 24V supply to the spindle fan or I/O signals.
• Power Surge: A lightning strike or massive surge from the utility grid.

Solution

1. Locate the Fuse: Look inside the drive (through the vents or by removing the faceplate). You might see a large black fuse or a small clear glass fuse depending on the generation.
2. Check for Shorts (Crucial): NEVER just replace the fuse and turn it on. Fuses blow for a reason. Use a multimeter to check the resistance across the DC Link terminals (P and N). If it reads near 0 Ohms, the drive is dead. Replacing the fuse will just cause it to blow again instantly (and dangerously).
3. Replace Drive: In 90% of SP9003 cases, the fuse blew to protect the building because the drive module is already destroyed.