Troubleshoot the Fan Tray and Impeller Assemblies

To troubleshoot the fan tray and impeller assemblies, follow these guidelines:

• If the red alarm LED on the craft interface lights, check the LCD on the craft interface for the source of the problem. The display reports the number of alarm conditions and the source of each alarm. For a list of messages, see Hardware and Interface Alarm Messages.
• Issue the following CLI command for more information about the source of an alarm condition:

user@host> show chassis alarms

• Issue the following command to check the status of the fans and impellers:
• To check the status of the impellers and fans, issue the show chassis environment command. The output refers to the Top and Bottom impellers and to the individual fans in the fan tray as the Rear Left Fan, Rear Center Fan, and Rear Right Fan:

user@host> show chassis environment

Class Item                   Status     Measurement

Fans  Top Impeller           OK         Spinning at normal speed

      Bottom Impeller        OK         Spinning at normal speed

      Rear Left Fan          OK         Spinning at normal speed

      Rear Center Fan        OK         Spinning at normal speed

      Rear Right Fan         OK         Spinning at normal speed

For further description of the output from the command, see the JUNOS Internet Software Operational Mode Command Reference: Protocols, Class of Service, Chassis, and Management.

• Place your hand near the exhaust at the upper rear of the chassis to determine whether the impellers and fans are expelling air.
• If both power supplies have failed, the system temperature might have exceeded the threshold, causing the system to shut down. See All LEDs on Both Supplies are Off.
• If the LCD on the craft interface reports failure of only one impeller and the other impellers are functioning normally, the impeller is probably faulty and needs to be replaced. For replacement instructions, see Maintain and Replace Cooling System Components. For instructions about returning a faulty component to Juniper Networks, see Return the Router or Its Components.
• If one of the fan assemblies fails, look at the fan to determine whether the blades of the fan are rotating. Individual blades are not distinguishable when the fan is rotating at normal speeds.