Why are fans on a CE12800 series switch running at full speed

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The following situations may cause full-speed running of fans on a CE12800 series switch:

1. The cards in a zone overheat, and fans in this zone must run at full speed to lower card temperature.
2. Some cards in a zone have all temperature sensors failed and card temperature cannot be obtained.
3. Management channels in a zone are interrupted, so the system cannot obtain card temperature in this zone.
4. The management channels of some fans are interrupted, so the speed of these fans cannot be adjusted based on real-time card temperature.
5. If any of the preceding situations occurs in a zone, fans in the adjacent zones with running cards also run at full speed.
6. Fans also run at full speed when you set the fan speed to the highest using the set fan-speed command.
You can see alarm messages on the network management system in situations 1 to 5.

Other related questions:
Why are fans on CE8800&CE7800&CE6800&CE5800 series switch running at full speed
The following situations may cause full-speed running of fans on a CE8800&CE7800&CE6800&CE5800 series switch: 1. There is only one fan module on the switch. In this case, the switch generates fan module absence alarms for idle fan slots, and fans in the present fan module work at full speed. 2. Power modules and fan modules in the switch use different airflow designs. In this case, the system reports alarms about inconsistent airflow directions of the power modules and fan modules. Inconsistent airflow directions between power modules, fan modules, or between power modules and fan modules degrade system reliability when the switch needs to work in a high-temperature environment for a long time, and shorten service life of the switch. 3. The management channels of some fans are interrupted, so the speed of these fans cannot be adjusted based on real-time equipment temperature. 4. Fans also run at full speed when you set the fan speed to the highest using the set fan-speed command.

Fan speed adjustment for S series fixed switch
S series fixed switches (except S1700 switches) use any of the following heat dissipation modes: forced heat dissipation, intelligent heat dissipation, and natural heat dissipation. 1. Natural heat dissipation applies when a switch does not have a built-in or external fan. 2. In intelligent mode, the fans start to operate only when the ambient temperature goes higher than a specified value. 3. In forced mode, fan modules keep working when the switch is running and automatically adjust the speed according to the switch temperature. For fan-equipped switches that run V200R003C00 or a later version and use forced heat dissipation or intelligent heat dissipation, you can run the set fan speed-adjust threshold minus command to set the temperature threshold for fan speed adjustment. For switches using forced heat dissipation, the new threshold is the default temperature threshold minus threshold-value, and the temperature thresholds for increasing and decreasing fan speed are both reduced. For switches using intelligent heat dissipation, this command reduces the temperature thresholds for starting and stopping the fan.

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