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Troubleshoot the
Power System
LEDonBothSuppliesIsOff
If the LED is of
f on both power supply faceplates, either someone has switched off power to
the router or the system temperature has exceeded the acceptable maximum. In the latter
case, the Routing Engine shuts down both power supplies. There is no power to the router, so
no LED is lit, i
ncluding the alarm LEDs on the craft interface.
Excessive system temperature is almost always caused by excessive environmental
temperature
. Correct the environmental temperature before repowering the router.
LED on One Supply Is Off
If the L ED on o
ne power su pp ly is off, but the LED on the other sup ply indicates that it is
functioning properly, perform the following diagnostic procedure:
1. Check the red
alarm LED on the craft interface:
• If it is lit,
issue the following CLI command for information about the cause of
an alarm condition:
user@host> show chassis alarms
For a list of messages that can appear in the output, see “Hardware and Interface
Alarm Messa
ges” on page 122. A common cause of power supply shutdown is that
the temperature of the power supply or another router c omponent has exceed
the maximum limit.
• If the red alarm LED is not lit, check that the power switch is in the ON position on
the power supply faceplate.
2. Replace the faulty power supply with a spare. For instructions, see “Replace an AC Power
Supply” on page 98 and “Replace a DC Power Supply” on page 104. If the LED lights
correctly
on the spare, the original power supply is faulty. Return it to Juniper Networks
for replacement, as described in “Return the Router or Its Components” on page 163.
3. If the spare power s upply also does not work, connect the router to a different power
source. You might also try replacing the power cord (on an AC-powered router) or power
cable (on
a DC-powered router). For instructions, see “Replace an AC Power Cord” on
page 103 and “Disconnect and Connect DC Power” on page 108 (you do not need to
disconnect and reconnect the grounding cable on a DC-powered router).
4. If you cannot determine the cause of the problem or need additional assistance, see
“Junipe
r Networks Technical Assistance Center” on page 124.
126 M5 and M10 Internet Routers Hardware Guide