258 Troubleshooting
a. Open loop (curve A) is fan speed control (FSC) curve with default mode.
b. Refer to the Fan Controller Firmware Response section for more information.
c. Open loop (curve B) is FSC curve with emergency mode.
d. Open loop (curve C) is FSC curve with fan failure mode.

Fan Controller Firmware Response

Refer to the tables below when troubleshooting enclosure fan noise and for the FC firmware responses to the possible PWM duty cycle values. Table5-2 lists the FC firmware responses in case scenario 1:• Interval 1 — If the calculated value of the PWM is higher than 100%, the FC firmware will send a signal to the fan to operate at 100% duty cycle and trigger sled throttling. • Interval 2 — If the calculated value of the PWM duty cycle is still higher than 100% again, the FC firmware will send a signal to the fan to operate at 100% duty cycle and trigger sled throttling for 1 hour.
Two f an
modules fail
System throttling,
After 90 seconds has
passed, the system will
be forced to shut
down
System
throttling,
After 90
seconds has
passed, the
system will be
forced to shut
down
System throttling,
After 90 seconds has
passed, the system
will be forced to shut
down
System
throttling,
After 90 seconds
has passed, the
system will be
forced to shut
down
Three fan
modules fail
System force
shutdown
System force
shutdown
System force
shutdown
System force
shutdown

Table 5-2. Case Scenario 1

Interval (30 secs) PWM Results Fan Controller Firmware Action
Interval 1 PWM > 100% 1
Sets PWM = 100%
2
Sled throttling mechanism is active
Interval 2 PWM > 100% 1
Triggers sled throttling for 1 hr.

Table 5-1. Fan Module (Fan Controller Firmware) Thermal Behavior Per Sled

Fan Module
Status
BMC (Processor/Memory)/Server Enclosure Temperature Status
OK/OK OK/Fail Fail/OK Fail/Fail