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  • 1.  Airflow direction mismatch alarm

    Posted 08-29-2013 08:02



    we've got an EX4500 Switch with Front-to-Back chassis fan and one power-supply, which is also Front-to-Back cooled. Now we've inserted a 2nd power-supply which is Back-to-Front. We just opened the power-supply and turned the fan, so its also Front-to-Back now. Problem now, the Device is giving a major alarm, because of the mismatching airflow direction.


    2013-08-29 11:53:43 UTC Major FPC 0 Airflow direction of PSU and Chassis fan are not matching


    Is there any way to disable this alarm? Or is there maybe a jumper or something inside the power-supply, to correct to airflow direction reported to the device itself?


    thanks for any advices!



  • 2.  RE: Airflow direction mismatch alarm

    Posted 08-29-2013 11:22

    There are two differet SKUs on the power supplies:






    Reversing the fan inside the power supply is not only what I would assume to be against Juniper's recommended procedures, but that's not going to change the SKU that is burned into the component (and thus reported to the chassis).


    Wherever you bought the -BF power supply from, I would ask if they can exchange it for the -FB.  Put the fan back the way it was and hopefully you didn't leave any signs of tampering.  Smiley Indifferent

  • 3.  RE: Airflow direction mismatch alarm

    Posted 07-06-2018 05:30

    What is the Juniper command used to clear the alarm from the switch (EX4300)?

    Here is the displayed alarm message: Major  FPC 0 Fan & PSU Airflow direction mismatch

  • 4.  RE: Airflow direction mismatch alarm

    Posted 07-06-2018 07:25



    If there's a genuine mismatch in air flow, then there's no way to clear the alarm.


    However if you have managed to tamper and reversed the polarity then the alarm might clear.  If there is no mismatch physically and yet you see this alarm, please try the following command:


    set chassis alarm management-ethernet link-down ignore


    There was a cosmetic glitch in some cases that causes the management link down to be read as an airflow mismatch alarm PR1327561 (resolved on 17.2).


    Note that physically modifying the PSU isn't recommended and replacing it with the right part is best; especially if you may need an RMA some day.




    If this solves your problem, please mark this post as "Accepted Solution."
    Kudos are always appreciated :).