Description

When a fan tray is installed and after it is fully seated, users may observe that the fans are not rotating and their rotations per minute (RPM) are indicated as being 0.

This articles states that software code has been modified to reset the power circuitry of the fan tray so that the fans rotate as soon as they are inserted fully.

Symptoms

When a fan tray is installed and after it is fully seated, users may observe that the fans are not rotating and their rotations per minute (RPM) are indicated as being 0:

user@re0> show chassis alarms
1 alarms currently active
Alarm time               Class  Description
2023-06-13 01:39:45 UTC  Major  Fan Tray 1 Failure

user@re0> show chassis fan            
      Item                      Status   % RPM     Measurement
<>
      Fan Tray 1 Fan 0          Failed   0%        0 RPM
      Fan Tray 1 Fan 1          Failed   0%        0 RPM
      Fan Tray 1 Fan 2          Failed   0%        0 RPM                    
      Fan Tray 1 Fan 3          Failed   0%        0 RPM                    
      Fan Tray 1 Fan 4          Failed   0%        0 RPM                    
      Fan Tray 1 Fan 5          Failed   0%        0 RPM                    
      Fan Tray 1 Fan 6          Failed   0%        0 RPM                    
      Fan Tray 1 Fan 7          Failed   0%        0 RPM                    
      Fan Tray 1 Fan 8          Failed   0%        0 RPM                    
      Fan Tray 1 Fan 9          Failed   0%        0 RPM                    
      Fan Tray 1 Fan 10         Failed   0%        0 RPM                    
      Fan Tray 1 Fan 11         Failed   0%        0 RPM                    
      Fan Tray 1 Fan 12         Failed   0%        0 RPM                    
      Fan Tray 1 Fan 13         Failed   0%        0 RPM                    
      Fan Tray 1 Fan 14         Failed   0%        0 RPM                    
      Fan Tray 1 Fan 15         Failed   0%        0 RPM                    
      Fan Tray 1 Fan 16         Failed   0%        0 RPM                    
      Fan Tray 1 Fan 17         Failed   0%        0 RPM                    
      Fan Tray 1 Fan 18         Failed   0%        0 RPM                    
      Fan Tray 1 Fan 19         Failed   0%        0 RPM                    
      Fan Tray 1 Fan 20         Failed   0%        0 RPM                    
      Fan Tray 1 Fan 21         Failed   0%        0 RPM

Solution

Software code has been modified to reset the power circuitry of the fan tray so that the fans rotate as soon as they are inserted fully. PR1745299 contains the fix for devices that run Junos and PR1742174 + PR1767111 contains the fix for devices that run Junos EVO. We suggest that you upgrade to an appropriate version to resolve the stated problem.

Note: An event-script is also available for those who cannot upgrade software versions immediately. Contact Support for more details.

To detect Part Numbers, refer to KB9475 - Mapping between FRU part numbers and model numbers [juniper.net].

Modification History

2024-02-20: Article created
2024-03-22: Added info about PR1767111