Cisco 10000 Series Routers

Field Notice: Cisco 10000 ESR: Erroneous Fan Alarm

September 7, 2001

Products Affected


Top Assembly

Part Number





Problem Description

An erroneous fan failure may be reported when redundant performance routing engines (PREs) are installed in an Cisco 10000 Edge Services Router (ESR) system. This problem has only been seen when the system was running in a high temperature environment. (40 C).


The optoisolator from the blower which controls the BLOWER_ALARM1 signal pin may not sink enough current to drive the signal low when there is a second PRE present. The efficiency of this optoisolator is also degraded at high temperatures.

When not driven low, the resulting voltage of the BLOWER_ALARM1 signal will float at about 1.25Vdc, which is considered a logic "1" (or ON).

Problem Symptoms

Although all fans are still operating and no alarm LEDs are lit on either PRE, the external "minor alarm" relay can be triggered. This results in a minor alarm indication to the user.

In addition, a show environment command from the console indicates that a partial fan failure is present. For example:

ESR10000#sh env
     Temperature normal: chassis inlet measured at 25C/77F
     Temperature normal: chassis core measured at 42C/107F
     Fan: partial failure
     Power Entry Module 0 type AC status: OK 


There is no workaround to this issue.

The solution is to replace the ESR-BLOWER assembly with one that has the necessary H/W changes. (See the How To Identify Hardware Levels section of this field notice for more specifics).

How To Identify Hardware Levels

Several item numbers have been changed as a result of this Engineering Change Order (ECO). Two of these numbers are visible on a label on the outside of the assembly.

The vendor part number was changed from 74-0902-02 to 74-0902-03. This number is visible on the McLean label on the right side of the assembly.

The CLEI code for the blower was changed from BAPQAC8YAA to BAPQADYYAA. This number is visible on a white label on the front of the assembly.

Either of these methods can be used to determine if the blower assembly has the hardware changes to address this issue.

Note:?You cannot determine the hardware revision of the ESR blower assembly with any CLI.

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods: