> Source: [sk153692](https://support.checkpoint.com/results/sk/sk153692)

# sk153692 - Abnormal chassis fans rotation speed

| Property | Value |
|----------|-------|
| Solution ID | sk153692 |
| Date Created | 2019-05-20 |
| Last Modified | 2019-05-22 |
| Technical Level | General |
| Products | Scalable Platforms |
| Versions | R82, R81.20 |
| OS | Gaia |
| Platform | 41000 (EOL), 44000, 64000 |

## Symptoms

- * An alert is sent that all chassis fans are rotating at full speed. After 3 minutes, the fans go back to normal rotation speed (below threshold).
* An alert is sent that some of the chassis fans are down. After 30 seconds, the fans are reported as up again.

## Cause

A momentary false reading of the fans' rotation speed by the CMM may cause two issues:

* If the CMM samples a fan speed sensor and the reading is below 486 RPMs:
  * It will set all fans to full speed.
  * When the reading is incorrect, normally the value will be zero (marked as 0xff in the CMM System Event Log).
  * In the next CMM sample (the interval is 2 seconds), the CMM will get the correct value and will start to decrease the fans' speed back to the normal speed.
  * The CMM will lower the speed level by one every 30 seconds.
* If the CMD (Chassis Monitor Daemon) samples a fan speed sensor and the reading is below 1000 RPMs:
  * The CMD will consider the fan as down and will send an alert.
  * In the next sample by the CMD (the interval is 30 seconds), the CMD will get the correct value and will consider the fan as up again.

## Solution

A new CMM firmware is available that addresses these issues:

* The firmware is available for all chassis types (N+1 / N+N).
* 64000, 61000 N+N, and 44000 users need to install CMM700 new firmware 3.70-rev6. The firmware is available in [R76SP.50 JHF](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk117633) starting take 105.
* 61000 N+1 and 41000 need to install CMM500 new firmware 3.70-rev6.1. The firmware is available in [R76SP.50 JHF](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk117633&partition=Advanced&product=Scalable) starting take 161.
* The new firmware implements a mechanism that buffers the readings of the fans sensors, when sampled. The buffer median is taken as the sensor value.
* To see the latest firmware available for all CMM types, refer to [sk93332](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk93332) (refer to the "***Hardware software revision***" section).
* Alignment of CMM and CMD lower thresholds for fans rotation speed.

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