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    Troubleshooting the Cooling System on the M40e Router


    The cooling system is not functioning normally.


    The router's cooling system comprises separate front and rear subsystems:

    The router’s cooling system comprises separate front and rear subsystems:

    • The front subsystem includes the fan tray located behind the cable management system and the impeller located behind the craft interface. They cool the FPCs, PICs, and midplane. See M40e Chassis Description.
    • The rear subsystem include upper and lower impellers in the rear of the chassis. They cool the SFMs, host module, PCGs, and power supplies. See M40e Chassis Description.

    The cooling system draws in room air through the air intake vent located at the front of the chassis below the cable management system. After entering the chassis, the air stream separates into separate flows for the front and rear subsystems, and the MCS monitors the temperature of each flow independently. For a graphic depiction of the airflow, see M40e Cooling System Description.

    For the cooling system to function properly, the clearance around the chassis must be sufficient for unobstructed airflow. See M40e Clearance Requirements for Airflow and Hardware Maintenance.

    During normal operation, the impellers and fans in the fan tray function at less than full speed. The MCS constantly monitors the temperatures detected by sensors on the midplane and router components, adjusting the speed of the fans and impellers as necessary. If the router temperature exceeds the acceptable maximum, the MCS turns off the power supplies. The following conditions automatically cause the fans and impellers to run at full speed and also trigger the indicated alarm:

    • A fan or impeller fails (red alarm).
    • One of the impellers 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).

    For more information about impeller-related alarms, see M40e Chassis and Interface Alarm Messages .

    To troubleshoot the fans and impellers, follow these guidelines:

    Published: 2010-10-28