I don't know the answer to your question, but would like to know myself. I have a couple of 2811s that keep complaining about the fan stopping and starting. Mine are not very old so I am not impressed with the longevity of these fans. I don't really want to change the whole unit out to fix a fan problem.
By the way, I spent 23 years with happy people myself - got axed after the merger with Compaq. I had a roommate from Sydney while in Cupertino for 11 weeks of training (1979) - long time ago.
Although I cannot see any relation with the p/n I am after,
Here it is teh output from a good router
Router#sh environment all
Main Power Supply is AC
Fan 1 OK
Fan 2 OK
Fan 3 OK
System Temperature: 21 Celsius (normal)
Environmental information last updated 00:00:01 ago
I was trying to find out which particular fan has gone faulty. Since u are suspecting Fan3 . this is the fan which is connected to power supply while the other two are connected to Motherboard.
I am having 2811 router with me , I have tried to open router but could not find any part code written on either of fans.
I think u need to replace the whole chassis .
The below link will help you to find the part number. I am sure it will help other friends also.
ACS-2811-FAN-1/2= CISCO2811 FAN #1 and FAN #2 Field Replacement Unit USD 25.00
ACS-2811-FAN-3= CISCO2811 FAN #3 Field Replacement Unit USD 25.00
From 3rd party
FAN 1 and 2 is usually a Sunon KDE1204PKVX or a NMB 1608KL-04W, these are the stats:
Size: 40x40x20 mm
Rated Voltage: 12V
Input Current: 0.12A
Input Power: 1.4W
Speed: 8200 RPM
Max Air Flow: 10.8 CFM
Max Air Pressure: 6.9 mmH2O
FAN 3 is either a DELTA FFB0412VHN, a NMB 1611KL-04W or a Sunon PMD120PQB1-A, these are the stats:
Size: 40x40x28 mm
Rated Voltage: 12V
Operation Voltage: 4.5V - 13.2V
Input Current: 0.16A (0.24A MAX)
Input Power: 1.92W (2.88W MAX)
Speed: 9500 RPM
Max Air Flow: 15.79 CFM
Max Air Pressure: 12.94 mmH2O
You can use any FAN that have the same specs, but be aware Cisco changed the pin configuration so you need to adjust it accordingly. I got a few stock Sunon MagLev GM1204PQV1-8A and they are perfect match for FAN 3, you just need to swap the Black and Red cable on the connector and they have been working flawlessly on my Cisco 2811 routers.
Using any 40x40mm FAN that fits will cause throuble if either Air Flow or the Speed are slower than the specs or if the
pin configuration does not match the Cisco OEM part.