Cisco GSR12/60 - 12012 Router -AnyLAN, SONET/SDH Installation And Configuration Manual page 64

Physical and Functional Overviews
A blower module controller card in the blower module monitors and controls the operation
of the three variable-speed fans. The variable-speed feature enables quieter operation by
allowing the blower modules to operate at less than maximum speed when doing so
provides adequate cooling to maintain an acceptable operating temperature inside the card
cage assembly.
Temperature sensors (two per card) monitor the internal air temperature. When the ambient
air temperature is within normal operating range, the fans operate at their lowest speed,
which is 55 percent of the maximum speed.
If the air temperature inside the card cage assembly rises, fan speed increases to provide
additional cooling air to the internal components. If the internal air temperatures continue
to rise beyond the specified threshold, the system environmental monitor shuts down all
internal power to prevent equipment damage from excessive heat.
If the system detects that one of three fans within a blower module has failed, it displays a
warning message on the console screen. In addition, the two remaining fans go to full speed
to compensate for the loss of the one fan. If another fan fails, the system shut downs to
prevent equipment damage.
A handle on the blower module provides a grip point for removing and replacing a blower
module. (See Figure 1-11.) Two LEDs (one green and one red), visible through the blower
module front cover, provide blower module status. The green LED, when on, indicates all
three fans are operating normally. The red LED should remain off during normal operation.
If the red LED is on, a fan failure or other fault has been detected in the blower module. The
fault can be one or more stopped fans or one or more fans running below speed, or the
controller card has a fault.
Note
Replacement Instructions (Document Number 78-4335-xx) contains detailed instructions
for removing and replacing a blower module. This configuration note accompanies every
blower module that is shipped from the factory as a FRU.
1-36 Cisco 12012 Gigabit Switch Router Installation and Configuration Guide
The configuration note Cisco 12012 Gigabit Switch Router Blower Module