Fans do not run. Make sure the fan tray is fully inserted into the chassis. Check input power connections. If connections are loose or their polarity is reversed, chassis does not receive power and fans do not run. Replace the fan tray.
Fans run but the system overheats.
Make sure that all intake and exhaust vents on the front, rear, and sides of the chassis are free of blockages. Make sure that the ambient temperature and other environmental factors in the system area are within the ranges specified in Table 1-1 . 3 . Make sure all cards, blank faceplates, and covers are in place. The cooling system cannot operate effectively unless the chassis is fully enclosed. Enter the show environment all command and check the results to see if individual fans have failed.