If you suspect a fan failure, perform these steps:
Check the LEDs. If all the LEDs are off, check the power to the switch. The fan could have failed due to a power problem.
Check the system LED. If it is amber, the system has detected a problem. If you cannot hear the fan operating, this could indicate a fan problem.
Note: If you are using a Catalyst 3524-PWR-XL, 2940, 2950 and 2955, 2970, 3550 or 3750 series switch, check the fan for failure by issuing the show environment fan command, as shown in this sample output: