Parameter 8901 is associated with the on Fanuc controllers. When a system fan fails, the controller typically triggers a "701 Fan Motor Stop" alarm, which can halt production.
While effective on systems like the 0i-C , newer controls like the 0i-F or 31i-B may not allow this software-based bypass for certain hardware fans. How to Change Parameter 8901
To achieve a result with Parameter 8901, you must understand its two bits and then apply the correct logic for your machine’s mechanical configuration.
You must provide an alternative cooling method, such as opening the electrical cabinet and using an external fan to prevent internal hardware damage. Restore Defaults: fanuc parameter 8901 better
[MDI Mode] ➔ [SETTING Key] ➔ [PWE = 1] ➔ [SYSTEM Key] ➔ [Search 8901] ➔ [Change Bit 0 to 1] 1. Enable Parameter Write
is considered "better" only in emergency situations where a machine must finish a critical part before maintenance can be performed. Situations to Use This Workaround:
| Method | Repeatability | Maintenance | Speed | Thermal Stability | |--------|---------------|-------------|-------|-------------------| | Dog + grid (8901.0=0) | ±5–10 µm | High (dog wear) | Slow | Poor (dog changes with temp) | | Dogless (8901.0=1, bits 4&7=1) | ±0.5–1 µm | None | Fast | Excellent (direct to encoder) | Parameter 8901 is associated with the on Fanuc controllers
The alarm is suppressed. This allows the machine to continue operating even if the system detects a fan failure. How to Use Parameter 8901 to Resolve ALM 701
The “better” setting typically refers to for most modern setups.
Once your replacement fan arrives, immediately change Parameter 8901#0 back to 0 . This reinstates the control unit's native safety netting, ensuring long-term hardware preservation. Comparative Analysis: Temporary Bypass vs. Root Cause Fix How to Change Parameter 8901 To achieve a
The table below outlines the trade-offs of using Parameter 8901 to bypass an alarm versus performing an immediate hardware replacement. Operational Factor Parameter 8901 Set to 1 (Bypass) Parameter 8901 Set to 0 (Standard/New Fan)
To help you troubleshoot this or implement other safety parameter optimizations, tell me:
Using Parameter 8901 to clear an alarm does not resolve the physical cooling failure. Operating a FANUC control system without adequate heat dissipation will permanently degrade memory modules and processors. Implement these critical defensive measures while waiting for replacement components: