Cisco Gigabit Switch Router 12008 Installation And Configuration Manual page 269

5 Tighten the fan tray captive installation screws.
6 Reinstall the air filter assembly.
If the left fan tray LED remains on after reseating the card cage fan tray, the unit is
faulty and should be replaced.
If the right fan tray LED on the CSC faceplate is on (amber), reseat the power
supply fan tray in the backplane, as follows:
Loosen the captive installation screw on the fan tray faceplate.
1
Grasp the fan tray by the captive installation screw and partially withdraw the
2
unit from the slot.
3 Firmly reseat the fan tray in the slot.
4 Tighten the fan tray captive installation screw.
If the right fan tray LED remains on after reseating the power supply fan tray, the
unit is faulty and should be replaced.
— If a fan tray still fails to operate as expected, a problem may exist with the DC-DC
converter on the CSC that powers the fan trays.
On system startup, note that the fans operate at maximum speed until IOS is fully
booted or if any fans fail or are absent.
Fan speed is determined by temperature sensors on the cards in the upper and lower
card cages and the power supplies. If an air temperature above the normal operating
limit is detected within the router, the MBus module on the CSC increases the fan
tray operating voltage. This higher voltage results in a corresponding increase in fan
speed, forcing more cooling air through the entire router enclosure.
•
The following message indicates that the system has detected an overtemperature
condition or an out-of-tolerance power condition inside the router:
Queued messages:
%ENVM-1-SHUTDOWN: Environmental Monitor initiated shutdown
The preceding message could also indicate a faulty component or a faulty temperature
sensor. Before the system shuts down, issue the show environment command or the
show environment all command. Either command displays information about the
internal system environment, including voltage measurements on each card for the
Troubleshooting the Cooling Subsystem
Troubleshooting the Installation 5-19