SV0444 Internal Fan Failure fault in Fanuc drive

SV0444 Internal Fan Failure fault in Fanuc drive

Description

The SV0444 alarm is straightforward but prevents the machine from running. It indicates that the internal cooling fan located inside the servo amplifier unit itself is not rotating at the correct speed or has stopped completely. Modern Fanuc Alpha i-series drives use "intelligent fans" with a third wire (tachometer signal). The drive monitors the RPM of the fan. If the RPM drops below a threshold due to dust buildup or bearing failure, the drive triggers SV0444 to prevent the drive electronics from overheating.

Cause

This is almost exclusively a maintenance/wear item.

• Dust and Oil Mist: Machine shops are dirty environments. Oil mist combines with dust to form a sludge that coats the fan blades and bearings, slowing them down or seizing them.
• Fan Aging: The small bearings in these fans eventually dry out and fail after years of continuous operation.
• Loose Connection: Occasionally, the small 3-pin connector connecting the fan to the drive's control board vibrates loose.

Solution

This is usually a "replace" rather than "repair" scenario, but temporary fixes exist:

1. Identify the Fan: Look at the drive. There is usually a fan on top (external heat sink) and often a small fan embedded inside the plastic cassette (internal). SV0444 usually refers to the internal one, though it depends on the drive generation.
2. Cleaning: Remove the fan. Use compressed air and contact cleaner to blast out the sludge. Spin it by hand. If it moves freely, reinstall it and cycle power. This often clears the alarm for a few weeks while you order a spare.
3. Replacement: The fan must be replaced with a Fanuc-compatible unit. Standard PC fans often won't work because the drive looks for a specific tachometer signal/current draw. If you use a generic fan, the fan might spin, but the alarm won't clear.
4. Connector Check: Ensure the fan plug is seated firmly on the PCB.