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Thread: Help with alarms ("401 x axis servo vrdy signal off and 701 fan motor overheat)

  1. #1

    Question Help with alarms ("401 x axis servo vrdy signal off and 701 fan motor overheat)

    I run a Tsugami bx12 with a Fanuc LE1 control. Its pretty old, from 1994 i think so I know older machines are usually quirky.

    The shop turned off the air yesterday at lunch and all the machines alarmed out with the "low air pressure" alarm. you have to turn off the machine to clear the alarm. So I turned it off and back on.

    When I turned it back on it booted with the alarm "401:x axis servo vrdy signal off" (or something pretty close to that) on all my axises (x1 z1 c1 y1 b1 x2 z2) Ive gotten this alarm in the past and the only way ive found to clear it is turn off the breaker, wait somewhere between 30 mins and overnight then turn it back on and it is magically ok.

    so that happened yesterday. I turned it on today and as I expected the 401 alarm was gone, however the "701: fan motor overheat" alarm was up. do I have a bad temp sensor? the breaker was off all night. yesterday I turned the machine on a couple times after lunch and the 701 came up, sometimes with the 401 alarm, sometimes just the 701.

    So, my questions are:
    1. Is there a faster/better/correct way to clear the 401 vrdy signal off alarm?
    2. Is there any way to clear the 701 fan motor alarm? is my temp sensor dead? is there any way I can check without a VOM? can I bypass or override this any way?

    Thanks for any help!

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    Swiss Process Engineer / CNC training consultant

  2. #2


    so after turning it off and on a couple more times the alarms finally cleared so my problem is gone for time moment, however I hate problems that randomly occur and randomly fix themselves. So if you have any thoughts on how to fix/clear those alarms feel free to suggest anything


    Swiss Process Engineer / CNC training consultant

  3. #3


    Could be the spindle motor fan, or the fans on the axis amps/power supply. I'm not sure what that control is to look it up. If it has Alpha amps, should have a code on the display of those.

  4. #4


    Im randomly getting the 701 fan overheat alarm again. Is there any way to diagnose what is triggering it? the only fans I see are a pair that intake cool air into the electrical cabinet. They spin very freely and arent blocked.

    any thoughts?

    Swiss Process Engineer / CNC training consultant

  5. #5
    Join Date
    Jun 2010


    FANUC CNC controls since the 1990s (16, 18, 21, 0i, etc) contain 24VDC cooling fans in the CNC logic rack or CNC assembly (yellow plastic box). These fans have a 3 wire lead assembly (24V, 0V, Alarm). The CNC monitors the alarm signal and will post the 701 if any of these fans are reporting an alarm condition. The 701 alarm is not related to any spindle motor fans, drive amplifier fans, or external cabinet enclosure fans.

    8901 bit 0
    (FAN) A fan motor error is:

    0 : Detected. (When the fan motor error is detected, an overheating alarm

    1 : Not detected. (Use inhibited)

    The 701 alarm indicates that a fan has failed or running very slow. You should exchange the fans (I would do all of them as they are fairly cheap).

    Setting the above parameter will disable the alarm check. Caution-- Most people will set the bit, forget to change the fan and then eventually burn up a CNC module / board . Do with it what you must....

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