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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:
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 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
The LED that indicates normal operation for the component fails to light.
The appropriate CLI
show chassis environment
component is installed but is not receiving power.
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.
command indicates that the
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Table of Contents
Troubleshooting
