Troubleshooting the Front and Routing Engine Fan Trays

The three fan trays in the front of the router and the fans behind the Routing Engine panel at the rear of the router draw in room air to cool router components. Temperature sensors on the components detect temperatures above the acceptable range. Fan failure or an excessive temperature condition triggers the red alarm LED and the corresponding alarm relay contact on the craft interface. If the temperature passes the acceptable maximum, the Routing Engine turns off the power supplies.

To troubleshoot the fan trays, follow these guidelines:

• To check the status of the fans in a fan tray, issue the show chassis environment command. The output includes an entry for each fan tray, as shown in this example:
  user@host> show chassis environment

  Class Item                Status  Measurement
  ...
  Fans  Rear Fan            OK      Spinning at normal speed
        Front Upper Fan     OK      Spinning at normal speed
        Front Middle Fan    OK      Spinning at normal speed
        Front Bottom Fan    OK      Spinning at normal speed
  ...
  
  

  The row labeled Rear Fan reports the status of the Routing Engine fan tray and the other three rows report the status of the front fan trays. For further description of the output from the command, see the JUNOS System Basics and Services Command Reference.

• If one of the fan trays fails, determine whether you can distinguish individual blades in a fan—this is not possible when the fans are rotating at normal speed.
• If a front fan tray seems to have failed, move it to another bay. For information about replacing a front fan tray, see Replacing a Front Fan Tray.
  • If the fan tray does not work in the other bay, it is probably faulty and needs to be replaced. For instructions about returning a faulty component to Juniper Networks, see Contacting Customer Support and Returning Hardware.
  • If the fan tray works in another bay, there is probably a problem with power connectivity from the midplane. Contact JTAC for assistance.