Most Common Alarm Codes for Fanuc Servo Amplifiers (Indicated on the Status Display)

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Most common alarm codes found by Repair Zone technicians during repair.

When your CNC machine suddenly stops working what is the first thing that you do?  Probably open the cabinet and check the controller or amplifier?   If your machine is equipped with Fanuc Automation components, you probably check the status display on your Fanuc servo amplifier and see a number displayed?

These numbers are called alarm codes, or error codes.  There could be 9 possibilities.  The drive and amplifier technicians at Repair Zone use these alarm codes, also called fault codes, to help them troubleshoot during a repair.  When repairing Fanuc amplifiers, many times our technicians see the same fault codes come up.  Here is a list of the most common Alarm codes found on the status display on C-Series, Fanuc servo amplifiers:

Alarm Code #1

Overvoltage alarm (HV).  If DC voltage of main power supply is abnormally high, overvoltage alarms occurs (HV level: 430V DC).  Alarm occurs when regenerative discharge resistor is disconnected.  For 200V AC input, main circuit voltage is 283V DC (200 x 1.414).  Discharge operation is started at voltage of main circuit voltage plus 60V.

Alarm Code #3

DC link undervoltage alarm (LVDC).  Alarm occurs if DC voltage of main circuit power supply is abnormally low (LVDV level: 120V).  *Causes may include power supply voltage (+15V) being 10Vor lower and driver module PCB not inserted normally.

Alarm Code #8

Overcurrent alarm (HCL).  Alarm occurs when abnormally high current flows in main circuit of 1-axis amplifier or in main circuit of L axis of 2-axis amplifier.  *Causes may include faulty IC, abnormal PWM signal, faulty motor, and grounded wiring.

Alarm Code #2

Control power supply undervoltage alarm (LV5V).  Alarm occurs if control circuit power supply voltage (+5V) is abnormally low (LV5V level: 4.6VDC).

Alarm Code #5

Excessive regenerative discharge alarm (DCOH).  Alarm occurs when average regenerative discharge energy is too high.  *Causes may include operation of thermostat for regenerative discharge resistor or thermostat between (15) and (16) on terminal block T1; this operation results from too frequent acceleration/deceleration operations.

If you have any questions or need assistance, please call 989-922-0043.  To view our Fanuc Amplifiers in stock and repair capabilities at RepairZone, click here:

Fanuc Servo Amplifiers


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  1. I wont to know the servo alarm un the machine

  2. Thank you
    My machine write code 8 and l reed what this mean but I dont know what I do
    Please help me what I do

  3. Hi Safwat,

    Thank you for your question. Alarm code 8 is a L-axis over-current alarm(HCL).
    This alarm occurs if an abnormally high current flows in the L-axis motor.

    If you meg the motor and the cable and they are good, then it is probably out of spec components on your drive and it will have to be repaired.


    Jade York

  4. What does status d on my servo amp mean and how would i correct it Thanks Russell

  5. Hello. The amplifier (AC SERVO AMP C series) has a 3 on the status. This amp & the servo motor has been changed out approx. 1 month ago. What else should I be looking for?

    • Hi Scott,

      Sorry I missed your question. This may sound funny but many times people don’t engage the breaker switch on the top of the drive. Other cases point to a bad cable from the motor to the drive.


      Jade York

  6. Good morning.

    I have a old 2 T fanuc controller and after the material jammed I got a alarm 00172 I tried setting all overloads but no response from the machine , rapid and feed work but no rotation or collet closing.


  7. I have a CNC Milling Machine and I don’t find the origin of this Alarm code in the Manual .
    The Alarm 60M5-04 , anybody who can help me please.
    Product: V-CNC 500
    Model: EKT
    Serial: 7085-f00-KH0020
    Cinaninnati Milacron INOVA Company

    Thank’s in advance.
    I’m in Mexico ( Juarez ,Chihuahua MX )

    • Hi Martin,

      Unfortunately, I could not find any information on this. You should consult with Cincinnati Milacron OEM for help.


      Jade York

  8. My cnc machine is give the massage over voltage in DC-bus/DC link(fo2) so how to solve this problem
    It is bottero cnc

    • Hello Saurabh,

      Many times when you get a over-voltage, it is caused by either the servo motor or the IGBT is bad in your power supply. To be more accurate, I would need the manufacturer and model number of the drive.


      Jade York

  9. god evening
    i have Alarm Code 3 type/A06B-6066-H244
    power supply voltage (+15V) IS OK

    • Hello,

      Make sure the breaker switch is in the ‘on’ position on the top of the drive. This should solve your problem.

      Please let me know if I can help further.

      Jade York

  10. My machine servo amplifier A06B-6079-H204 A and shows alarm 2 in status in morning when machine starts after 3 hrs. off due to shift change. In day time it not shows any alarm. Is this is drive control PCB related alarm and control card need to repair.
    Please advise via mail id.

    • Hello Jagdeep,

      #2 alarm means the drive is not getting low control voltage. When alarm occurs, check for 24vdc at CX2A. If good then drive has components out of spec causing the alarm. The drive will have to be evaluated. If it is not getting 24vdc, then your problem is your power supply or cable. You can send the drive or power supply, whichever is malfunctioning, to us at Repair Zone for a free evaluation:

      Repair Zone
      615 Andre Street
      Bay City, MI 48706


      Let me know how I can help further.

      Jade York

  11. My fanuc showing #5. Error what can i do, i already change all three pcb and change power supply dc and the voltage is oke but still showing #5

    • Hello Anggriyan,

      The customer states the DC voltage is good at the drive which means there is an internal problem in the drive itself. The Drive will have to be sent in for evaluation and repair.

      We would be happy to evaluate it for you for free! You can ship it to:

      Repair Zone
      615 Andre Street
      Bay City, MI 48706


      Jade York

  12. Hi

    We have an injection molding machine . The robot movement is controlled by fanuc servo unit. When robot power is on, it shows ‘0’ ie ready but when we tried to move the robot it shows not ready ‘ – ‘ sign. The machine HMI shows alarms.
    1. General Servo fault
    2. Robot contoller, amplifier or motor alarm.
    Could you please help..

    • Hello George,

      Your issue may be the motor, or it could be a cable, or the amplifier. You can usually narrow it down to one of them by swapping out components and trying them in a different axis. Once you find what isn’t working, you can send it in to get verified and evaluated. Repair Zone will do it free of charge, and provide a repair quote. Let us know and we can assist you.


      Jade York

  13. Hi
    We have a Fanuc power mate H and there a LED indication S1,S0,WD and EN. The S1 LED is red now . What that indication means. Could you please help us..

    • Hello George,

      Thanks for your question. From where I am standing, most likely it is a connection/communication issue. Check (JS1A to JS1) and (JX1B jumper or connection to next drive). I hope this works for you. Please let us know if it does, we’d love to hear back!


      Jade York

  14. hi dear my machine give me (8.) alarm can you help me what i can do

    • Hi Andrawes,

      Thanks for your question today. The #8 fault is abnormally high current flows in the L-axis motor, a very common fault. As long as the cables and motor tests good, you can isolate the 8 fault to having a blown IGBT or other bad components on the A06B-6079-H106 Fanuc amplifier. A solution would be to send it in to Repair Zone for a free evaluation and quote for repair.

      Repair Zone has seen many of these models in for repair through the years and has had great success! or (989)922-0043

      Best Regards,

      Jade York

  15. Have an a06b-6111-h030#570 with an alarm code 15. I know its not my ladder we have been running this machune for 10 years. With no issues. How do I figure out if its the magnetic contact or the I/o unit

    • Hello Adam,

      Thanks for your question. The best thing to do is go over the following steps:

      Alarm code 15
      In output switching control or spindle switching control, the switching
      operation sequence was not executed correctly.
      This alarm is issued if one second or more elapses from the transition of
      a switch request signal (SPSL or RSL) until a power line state check
      signal (MCFN, MFNHG, RCH, or RCHHG) makes a transition.
      Troubleshooting when this alarm is issued
      (a) The magnetic contactor (switch unit) for power line
      switching is faulty.
      If the contact is inoperative, check the power supply of the
      magnetic contactor. If the magnetic contactor is still
      inoperative, replace the magnetic contactor.
      (b) The I/O unit or wiring for checking the contact of the
      magnetic contactor is faulty.
      If a defect is found in the I/O unit or wiring, replace the I/O
      unit or wiring.
      (c) The sequence (ladder) is incorrect.
      Modify the sequence so that switching is completed within 1

      Let us know if I can help further. If you need professional service on the unit, we can help.
      go to and get your repair started.

      Jade York

  16. Hi, I have alarm #2 on my Fanuc servo amplifier (A06B 6079 H206) when the main power is first switched on in the morning. If I leave the power on for about 30 sec switch the main power off then on after a few seconds the alarm goes away. Is there maybe a battery going bad in or is the amplifier maybe on is way out. The backup encoder position batteries on the cabinet door are good. Thanks

    • Hello Carl,

      To answer your question about the #2 alarm on your A06B-6079-H206, if there is approximately 24vdc at the CX2A connector then the drive has components out of spec and will need to be reconditioned. We can certainly help you with that. Go to and get your repair started.
      Good luck to you and I hope we can help!


      Jade York

  17. Good Afternoon, We have a 2000 Takisawa EX-108 with a Fanuc 21i-T control, that I would like to get back into production. It has an error code #24 on the Spindle Amp, the book says that it is a communication error so have been looking for bad connections or broken wires. So far nothing. Any suggestions would be appreciated.

    Lowell Kenney

    • Hello Lowell,

      Thanks for reading The Machine Runner Blog! AL-24 is a communication error to Spindle connector JA7B. If there is a new or known good cable in place then swapping out spindle amplifiers would be the next step. (If spare is available.) Some aged or out of spec components in the Spindle amplifier can cause alarms. The Amplifier can be sent in for an evaluation.

      Our website,, is the portal to our nationwide repair services. We would be happy to help with an evaluation of your Fanuc amplifier, if necessary.

      I hope this information was of some value to you.

      Thanks again,

      Jade York

  18. Hello.
    On my Wire cutting machine (robofil 440slp) i have a problem with Fanuc PSM model A06B-6114-H303(it is alpha i SV 20/20/20). On the display is the letter P and the two other SVM wont energize (there is a line in the middle). Do you have any suggestions for me please.
    Best regards Ivan

  19. Hello,

    We have FANUC ROBOCUT with 18i, 5 axes cnc. We have alarm #9. (with dot) .
    This alarm occured when ambient temp. is > 86 F . In machine cabinet is 100-104 F.
    (Hot summer and we have not air conditioning ) . When is about 68 F , this alarm not occurs.

    • Hello Marco,

      Thanks for your question today. Here are a couple of possibilities. The M or (Y) axis IGBT is weak or amplifier components are failing under the high temperature. The Fan must be functioning efficiently without too much contamination. The amplifier may be due for reconditioning. Sending your amplifier in to a reliable, cost-effective source like Repair Zone can get things running smoothly again. Here is a link to get you started with a free evaluation:

      I hope this helps!

      Best Regards,
      Jade York

  20. I have an older fanuc controlled machining center. I am getting alarm 56. I found that the fan was broken and so I replaced it. The new fan is operating perfectly but I am still getting the alarm 56. Any ideas?

    • Hi Daniel,

      Thanks for contacting us with your question. Alarm 56 is an inner cooling fan stop. The smaller fan located inside the yellow case is the fan that must be changed. If that was changed and there is still a fault, then there could be components out of spec, trace damage, or other issues.

      If you need further assistance, you can send your unit in to Repair Zone for a free evaluation.

      Repair Slip:

      Best Regards,

      Jade York
      Repair Zone

  21. Hi. No comment but a hopeful question. I have a fanuc turret spindle drive with a #12 alarm that will not clear with pwr. down and back up. I hope that you can tell me about the alarm.

    • Hi Pete,

      Thanks for your question. #12 alarm code is most likely an IGBT has a short. This would require changing shorted IGBT with a new one.

      If this is something that you need a help with, you can send it to Repair Zone for a free evaluation and quote.

      You can start your repair here:

      If you have another question, just let us know.

      Best Regards,

      Jade York

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