Catalyst C9300 loud fan with only 1 powersupply but "silent" with 2 powersupplies

[herrplarsson]

Hello!!

Maybe a stupid qustion but I have a question regarding the fan sound on C9300-48P/24P switches.

If i run the switches with only 1 powersupply the sound from the fans are very loud, how ever as soon as i connect power to powersupply 2 the fans go almost silent. I can then remove the power from one PS again and in seconds the fan sounds get really loud again so it has nothing to do with overheating or anyghing.

The other day I had 3 switches running in the same rack on 1 powersupply each and after I connected power to PS nr 2 on the 3 switches the fans got so silent I thought I blev a fuse and the switches died but that was not the case.

There is no heat problem with the switches running on 1 or 2 powersupplies and sometimes 2 PS is just unnecessary and not worth the cost but the sound of the fans on just 1 PS is not good either.

/Andreas

[Reza Sharifi]

Hi,

If the room is not hot for the fans to run high then having one PSU should be as quiet as 2. These switches usually run fine with one PSU. I would open a ticket with Cisco.  You may need to RMA the switch. 

HTH

[herrplarsson]

Hello Reza,

thank you for your reply!:)

The room is not hot at all, does not matter if I have the switches in a room with good cooling or if I have them on my workbench in "ordinary room heat".

Guess I should open a TAC/RMA or so since all my  9 switches of this model all sound/act the same way.

Regards

Andreas

[brettlarkins · Accepted solution]

I've found this to be true with several different 9300 switches now.

If I have 1 single power supply in the switch and powered, it's quiet.

If I have 2 power supplies in the switch and they are BOTH powered, it's quiet.

However, if I have 2 power supplies in the switch, and only ONE is powered, it's loud as heck and the fan's never quiet down.

I tried several versions of software, too, and they did not change this behavior.  Seems to be "by design", I guess.

[herrplarsson]

Hello Brettlarkins!!

I must say that it NEVER came in my mind to remove 1 of the 2 PS:s and just test with one PS inserted in the switch but did the same as you know and with the same result so THANK YOU for your tests and answer!!:)

Guess if you have 2 PS inserted in the switch both should be connected to power but still never crossed my mind that there should be any difference in fanspeed if I pulled out PS nr. 2!!!:)

Regards

Andreas

[brettlarkins]

You're very welcome... Thank you for creating the initial post, and good luck out there!

[cmarsh801]

I have a 9300 on my desk and I just downgraded it from factory install Fuji to the Cisco recommended stable Everest - 1 PSU and the fans sound weird, revving up and down ever so slightly.  Almost like the switch is haunted.   I am pretty sure this wasn't the case with the Fuji build.  Also, unrelated but was surprised to see the 25g interfaces disappear.  Here's what it displayed at boot:

interface TwentyFiveGigE1/1/1
^
% Invalid input detected at '^' marker.

interface TwentyFiveGigE1/1/2
^
% Invalid input detected at '^' marker.

This went away after I wrote mem on the new IOS Everest.

[pringleh]

You nailed it. Same exact scenario here. Thanks for the advice.