Juniper Networks M160 manual Juniper Networks Technical Assistance Center

M160 Internet Router Hardware Guide

A blown fuse can cause a component to fail even though it is correctly installed and the power supplies are functioning. Check for a blown fuse in the following circumstances:

The LED that indicates normal operation for the component fails to light.

The appropriate CLI show chassis environment command indicates that the component is installed but is not receiving power.

For instructions for replacing a blown fuse, see “Replacing a Fuse” on page 204.

Juniper Networks Technical Assistance Center

If you need assistance during troubleshooting, you can contact the Juniper

Networks Technical Assistance Center (JTAC) by e-mail or telephone.

See “Requesting Support” on page xxiii.

Troubleshooting the Cooling System

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 Figure 1.

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 Figure 2.

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 Figure 20.

For the cooling system to function properly, the clearance around the chassis must be sufficient for unobstructed airflow. See Clearance Requirements for Airflow and Hardware Maintenance on page 62.

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

212 Troubleshooting the Cooling System