Code EF4 (Alarm): External fault (input terminal S4)
Issue Description & Safety Warning
The Yaskawa A1000 AC Drive has triggered a critical External fault (input terminal S4) 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
Code type: Alarm / minor fault Manual section: Yaskawa A1000 Troubleshooting An external device has tripped an alarm function. Remove the cause of the external fault and reset the multi-function input value. Wiring is incorrect. - Ensure the signal lines have been connected properly to the terminals assigned for external fault detection (H1-□□ = 2C to 2F). - Reconnect the signal line. Multi-function contact inputs are set incorrectly. - Check if the unused terminals have been set for H1-□□ = 2C to 2F (External Fault). - Change the terminal settings.
Source: Yaskawa AC Drive A1000 High Performance Vector Control Drive Technical Manual (SIEP C710616 21H)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Yaskawa A1000 AC Drive Alarms
Yaskawa controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code EF4 (Alarm) on the A1000 AC Drive identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Yaskawa's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 280 Yaskawa A1000 AC Drive codes.
Have a better solution?
Help the industrial community by sharing your repair experience for code EF4 (Alarm).
Need a searchable reference for more Yaskawa A1000 AC Drive manuals?
We structure equipment manuals into searchable code, title, cause, solution, safety note, and source-reference data. Send a PDF and example searched codes when you need public pages, private search, or structured exports.
Space reserved for Google AdSense / Industrial Affiliate Links
Monetization target for 2026