What causes FANUC alarm 079?

Program was modified in memory after the external copy was made. File transfer corruption resulted in a byte difference between the two versions. Different line ending formats (LF vs CRLF) causing byte count mismatch. Program number or header format difference between the external and stored versions. Partial transfer of a previous edit left a modified program in memory.

How do I fix FANUC alarm 079?

1. Exit program comparison mode and check which program is more current. 2. If the external version is correct, delete the memory version and retransfer. 3. If the memory version is correct, update the external copy from memory. 4. Check for trailing spaces or end-of-block differences if programs appear identical visually. 5. Verify the transfer cable and interface settings if corruption is suspected.

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FANUC Controller

Program/G-code · Advanced · 30-60 minutes

Alarm 079

Fanuc Alarm 079 - PROGRAM NOT MATCH

Alarm 079 indicates a communication failure between the CNC and the serial spindle amplifier (αi spindle). This typically occurs due to fiber optic cable damage, incorrect parameter settings, or amplifier hardware failure. The serial communication uses high-speed fiber optic transmission which is sensitive to cable condition and connection integrity.

FANUCProgram/G-codeAdvanced30-60 minutes

079

Fanuc Alarm 079 - PROGRAM NOT MATCH

PROGRAM NOT MATCH

Root Cause Summary

Alarm 079 indicates a communication failure between the CNC and the serial spindle amplifier (αi spindle). This typically occurs due to fiber optic cable damage, incorrect parameter settings, or amplifier hardware failure. The serial communication uses high-speed fiber optic transmission which is sensitive to cable condition and connection integrity.

Safety

Spindle control lost

Causes and Fixes

1
Check DIAGNOSIS > SERIAL SPINDLE screen to verify if spindle amplifier is detected. Look for spindle axis presence and ready status indicators.
2
Inspect both fiber optic cables (transmit and receive) between CNC and spindle amplifier. Check for minimum bend radius (30mm for standard cables), kinks, or visible damage. Ensure cables are not routed near sharp metal edges.
Never look directly into fiber optic cable ends. Disconnect power before inspection.
3
Clean fiber optic connectors using approved fiber cleaning solution and lint-free swabs. Check connectors for dust, contamination, or physical damage on ferrule ends at both CNC JD1A/JD1B and amplifier CN1A/CN1B.
4
Swap transmit and receive fiber cables as a test. If alarm changes characteristics or shifts, replace fiber optic cable set. Use only Fanuc-approved fiber cables (A660-xxxx series).

DIY Feasiblemedium confidence

Call a technician if:

·CNC interface board replacement required
·Spindle drive internal repairs needed
·Parameter backup/restore required

Prevention

Regular cable inspection and cleaning
Maintain proper parameter backups
Keep spindle drive firmware updated
Monitor diagnostic screens during preventive maintenance

Common Mistakes

Changing parameters without backup
Ignoring cable shield grounding
Mixing analog and serial spindle parameters
Not matching CNC and drive communication settings

Related Alarms

078 080 081 435 436

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