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Troubleshooting the T320 Cooling System



Description: During normal operation:

  • Fans in both front and rear fan trays function at less than full speed.

  • The control boards constantly monitor the temperatures detected by sensors on the midplane and router components, adjusting the speed of the fans as necessary.


If the router temperature exceeds the acceptable maximum, the control board turns off the power supplies.

The following alarms and LEDs indicate a problem when:

  • A fan fails (red alarm).

  • One of the fan trays is removed (yellow alarm).

  • The router temperature exceeds the “temperature warm” threshold (yellow alarm).

  • The temperature of the router exceeds the maximum (“temperature hot”) threshold (red alarm and automatic shutdown of the power supplies).


To troubleshoot the fans, follow these guidelines:

  • If the red alarm LED on the craft interface lights, find the source of the problem by looking at the display on the craft interface. The number of alarm conditions, as well as the source of each alarm, appears on the screen.

  • Use the CLI to check the status of the fans. For example, you can issue the following command to get information about the source of an alarm condition:

    user@host> show chassis alarms
  • Place your hand near the exhaust vents at the rear of the chassis to determine whether the fans are pushing air out of the chassis.

  • If the DC OK LED on one or both of the power supplies is not lit, check the power supply fans to see if they are operating.

  • If all power supplies have failed, the system temperature might have exceeded the threshold, causing the system to shut down.

  • If the display on the craft interface lists only one fan failure and the other fans are functioning normally, the fan is probably faulty and you need to replace the fan tray, as described in Replacing a T320 Fan Tray.


Alarm Type

LCD Display Message

CLI Message



Fan Failure

fan-name Failure

Fans Missing

Too many fans missing or failing


Fan Removed

fan-name Removed

Temperature sensors


Temperature Hot

Temperature Hot

Sensor Failure

Temperature sensor failure


Temperature Warm

Temperature Warm