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Troubleshooting the MX2020 Cooling System

 

Problem

Description: The following alarms, LEDs, and other conditions indicate a problem with the cooling system:

  • A red alarm indicates that temperature of the router exceeds the maximum (“temperature hot”) threshold.

  • Automatic shutdown of the power system was caused by the temperature of the router exceeding the maximum (“temperature hot”) threshold.

  • A red alarm indicates that a fan failed.

  • A yellow alarm indicates that the router temperature exceeds the “temperature warm” threshold.

  • A yellow alarm indicates that one of the fan trays was removed.

  • One or more fans in a fan tray function at full speed. The CB-RE constantly monitor the temperatures detected by sensors on the midplane and router components, adjusting the speed of the fans as necessary.

Solution

To troubleshoot the cooling system:

  1. Place your hand near the exhaust vents at the back of the chassis to determine whether the fans are pushing air out of the chassis.
  2. If the red alarm LED on the craft interface lights, look at the craft interface display to find the source of the problem. The number of alarm conditions, as well as the source of each alarm, appears on the screen.
  3. If the craft interface display 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.
  4. 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

    For information about the alarms, see Table 1.

    Table 1: MX2020 Cooling System Alarms

    Component

    Alarm Type

    CLI Message

    Alarm Condition

    Solution

    Fans

    Red

    fan-nameFailure

    A fan has failed.

    Replace the fan tray.

    Temperature sensors

    Red

    Temperature Hot

    The chassis temperature exceeded the hot temperature threshold. If this condition persists, the router shuts down.

    • Verify that the room temperature is within acceptable limits.

    • Verify that there is sufficient air flow.

    • Verify that the cooling system in the chassis is operating properly.

    Temperature sensor failure

    A temperature sensor failed.

    Contact JTAC

    Yellow

    Temperature Warm

    The chassis temperature exceeded the warm temperature threshold.

    • Verify that the room temperature is within acceptable limits.

    • Verify that there is sufficient air flow.

    • Verify that the cooling system in the chassis is operating properly.