Fanuc ALPHA servo alarm 8, 9, A

Alarm 8, 9, A: ABNORMAL CURRENT

Any Fanuc servo amplifier that has an 8, 9, or A alarm indicates high current or short circuit in the amplifier, motor, axis card or cables, or mechanical obstruction. These alarms are relavenet to single, dual or truple channel servo amplifier modules.

Depending type of amp. Your looking for a 7 segment display such as these:

Alarm displayed points to the servo channel which is faulting:

  • AL. 8 = L Axis (1st axis on drive)
  • AL. 9 = M Axis (2nd axis on drive)
  • AL. A = N Axis (3rd axis on drive)

Note: if your CNC machine has 3 single axis amplifies, then all three will only alarm out with AL.8; a dual with either 8 or 9 and triple with any of the three alarms.

Please do not confuse these alarms for the 8. / 9. / A. which are IPM based alarms and normally the amplifier is the cause.

Six potential causes of 8/9/A alarms on amplifier.

  1. Mechanical issues on the axis i.e. binding, obstruction or brake rectifier not releasing.
  2. Fault on the amplifier
  3. Motor issues – bearings, windings, liquids, etc.
  4. CNC system axis card.
  5. Signal cable between CNC and drive (on appropriate channel) ignore if FSSB.
  6. Power cable between drive and motor.

CNC Tip:

Watch out for stupid claims about what causes alarm 8, 9 or A. Encoder faults are encoder faults; you will not get an AL. 8, 9 or A from encoder issue. Instead the CNC will fault with 3xx series pulse coder alarms and the drive will go not ready i.e. single bar!

We can test amplifiers, motors and dependent on the system the axis cards also. We also supply servo drives, motors and system axis cards.

We always recommend using the services of a trained CNC service engineer whom has the electronic and mechanical knowledge to deal with the Fanuc side of your machine tool.

The alarms above cover 6079, 6089, 6090, 6096 and 6097; in some cases later aiSV modules.

CNC are Fanuc specialists: Parts – Exchange – Repair – Test – Surplus

  • Exchange -> Emergency breakdowns; swap the bad for the good immediately. Order Monday to Friday 9am to 4.30PM to ship same day! 
  • Repair -> Save money avoid paying deposit, keeping your own unit with known history. Current clean, inspect, repair and test turnaround 24-48 hours (normal). 
  • Surplus -> Either for stock critical parts or for drives that are not repairable or exchangeable due to burn outs, corrosion, etc.

Find more alarm information at DNC the independent Fanuc specialists for Europe.