all fans must be operating or a failure will occur.

    environmental problems may initially appear to be problems with the fan tray. to help isolate a fan assembly problem, follow these steps:

    step 1 check the status led on the fan tray.

    1 if the led is off and the rest of the system is functioning, the fan tray is not getting power or is not seated correctly on the backplane.

    2 if the led is green, the fans are operating normally. there may be conditions impairing fan performance, but they are minimal in impact.

    3 if the led is red, one or more fans have failed.

    step 2 connect a terminal and determine the fan tray status shown by the show environment status cli command.

    step 3 look for system messages reporting a temperature problem or problem with the fans. individual messages may suggest different solutions. connect a terminal to the console port, and look for any of the following system messages:

    c4k_chassis-2-insufficientfansdetected

    c4k_chassis-2-insufficientfansshutdown

    c4k_iosmodportman-4-criticaltemp

    c4k_iosmodportman-4-fantraybad

    c4k_iosmodportman-4-fantraypartialfailure

    c4k_iosmodportman-4-fantrayremoved

    c4k_supervisor-3-fantrayreadfailed

    c4k_supervisor-3-fantrayseepromreadfailed

    c4k_supervisor-3-fantrayseeprominvalid

    c4k_iosmodportman-4-temphigh

    c4k_iosmodportman-4-tempundercritical

    c4k_chassis-2-overheatingshutdown

    step 4 determine whether the airflow is restricted or if the ambient temperature in the room is too warm.

    step 5 determine whether the power supply is functioning properly. see the “troubleshooting the power supply” section .

    step 6 verify that the fan assembly is properly seated in the backplane by loosening the captive installation screws, removing the fan assembly, and reinstalling it.

    step 7 restart the system.

    step 8 verify that all fans are operating. you should hear the fans at system start.

    step 9 if the system is still detecting a fan assembly failure, contact the cisco tac for assistance.