Troubleshooting The M120 Cooling System - Juniper Networks Hardware Manual

M120 Multiservice Edge Router Hardware Guide

Troubleshooting the M120 Cooling System

Problem
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See "M120 DC Power Supply LEDs" on page 32 or "M120 AC Power Supply LEDs" on
page 30.
The fans in a fan tray are not functioning normally. During normal operation, the fans in
each fan tray function at less than full speed. The CB constantly monitors the
temperatures detected by sensors and router components, adjusting the speed of the
fans as necessary. If the router temperature exceeds the acceptable maximum, the CB
turns off the power supplies. The following conditions automatically cause the fans to
run at full speed and also trigger the indicated alarm:
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:
If the red alarm LED on the craft interface lights, use the CLI to get information about
the source of an alarm condition:
about alarms, see "Alarm LEDs and Alarm Cutoff/Lamp Test Button on the M120 Craft
Interface" on page 24.
Use the CLI to check the status of the fans:
the CLI output lists only one fan failure, and the other fans are functioning normally,
the fan is most likely faulty and you need to replace the fan tray, as described in
"Replacing an M120 Fan Tray" on page 134.
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 "Alarm LEDs and Alarm Cutoff/Lamp Test Button
on the M120 Craft Interface" on page 24.
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 all power supplies have failed, the system temperature might have exceeded the
threshold, causing the system to shut down.
M120 Cooling System Description on page 32
Maintaining the M120 Air Filter on page 102
Maintaining the M120 Fan Trays on page 102
Replacing an M120 Air Filter on page 138
user@host> show chassis alarms
user@host> show chassis environment
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