Catalyst 2960X - Fan Speed High / Still says OK when Disconnected

[A388Flyer]

In pursuit of renewing my long expired CCNA, I decided to pursue to real (used) hardware for a home lab.

The switch itself boots and operates generally without issue, but the fan stays at max...  I would estimate it's probably 80db and can be heard in through two sets of closed doors.

For the heck of it, I decided to power it off, disconnect the fan and then see what kind of warnings I would get in CLI.  To my surprise I saw the following:

Switch>sh env all
FAN is OK
SYSTEM TEMPERATURE is OK
System Temperature Value: 37 Degree Celsius
System Temperature State: GREEN
Yellow Threshold : 58 Degree Celsius
Red Threshold : 68 Degree Celsius

The fan is definitely not OK if it's disconnected, it's too bad CLI doesn't report RPMs also.  The temp does ramp up from about 35C to 38C after a bit so temp sensor is definitely working (no load or anything connected).

It is probably a hardware failure, but if anybody has any suggestions that might get the unit to report on the fan properly, it would be appreciated.

[Reza Sharifi]

It could also be a software bug in the version of the IOS you are running. Was there anything in the logs before and after disconnecting the fan? If you got it used, you most likely don't have any support on that switch to download a different version of the software.

HTH  

[A388Flyer]

I didn't try hot plugging (or unplugging) the fan, just removed power before doing so.  Nothing unusual in the console in booting with or without the fan plugged.  The firmware was on 15.2(7)E3, downloaded the image for E6 and applied it.  No difference unfortunately.

[Jitendra Kumar]

Don't see any bug in the release note related to the FAN.

you can do one thing check the CPU its spikes. it is quite possible for CPU spike

show proc cpu history

https://www.cisco.com/c/en/us/td/docs/switches/connectedgrid/cg-switch-sw-master/software/release/notes/rn-15-2-7e3.html

[A388Flyer]

Thanks Jitendra.  I did try that on a few occasions, I have nothing other than the console cable (and power of course) connected to the switch and CPU is generally very low.

I might perhaps put my oscilloscope on the fan header and see if it's varying the voltage at all as the temp slowly rises in the unit.  Wish I knew however how IOS determines if the fan is OK or not... I think if a fan was disconnected I should not be seeing "OK" in sh env all

[A388Flyer · Accepted solution]

I think I am going to write this one off as an IOS bug... found a 2015 thread where someone noted FAN is OK on another 2960X despite it being disconnected.  As or the noise/fan speed... apparently I did not let it boot fully enough for it to spin down.

Stuck the switch in my closet, plugged it in, walked away and came back 10 minutes later and all that I can hear from the closet is a dull whisper.

Thanks all for the input.