I have a stack of cisco 3750 switch (c3750-48ps) which has 4 switches total. Out of 4 one of the switch is showing fan faulty and temperature faulty. I checked the switch and found out that the speed of the fan of that switch is higher than the speed of the fan of the other switches. How can i trouble shoot this or fix this?

  • 1
    I don't think there is a way of changing the RPM on the fan's. They are controlled by what the current ambient temperature is, and adjust RPM as needed. Some fan trays might have jumpers that allows you to switch between ambient temp control and full speed. To me it sounds like you have a fault and might want to look at RMA'ing the faulty switch.
    – SleepyMan
    Jul 1, 2016 at 9:16
  • Got it. Thats what i am thinking of too. Also, I am planning on a reboot just to make sure if the alert goes away by doing so, if not then i will be RMA'in it. Thanks for your help.
    – user25763
    Jul 4, 2016 at 17:06

1 Answer 1


Use the environment command as a starting point:

show env all

The first part of the output should be similar to:

FAN 1 is OK
FAN 2 is OK
FAN PS-1 is OK
FAN PS-2 is OK
System Temperature Value: 29 Degree Celsius
System Temperature State: GREEN
Yellow Threshold : 46 Degree Celsius
Red Threshold    : 60 Degree Celsius

In this example both chassis fans and both power supply fans are reporting all's normal. The system temp is good and I have 17 degrees to go before I reach temp warning.

If one fan is hosed it is very likely that system temp increased and the remaining variable-speed fan has picked up the pace to keep the switch cool.

  • Thanks for your answer. The above case is for the switch (3750x) with the separate fan module that can be easily removed and replaced. In my case the switch (3750) have built-in internal fan. And when i apply the commands, this is what i get; SWSTACK#sh env all FAN is OK TEMPERATURE is OK Temperature Value: 42 Degree Celsius Temperature State: GREEN Yellow Threshold : 58 Degree Celsius Red Threshold : 68 Degree Celsius This is the switch in the stack having faulty fan SWSTACK#sh env stack 4 SWITCH: 4 FAN is FAULTY TEMPERATURE is FAULTY POWER is OK RPS is AVAILABLE
    – user25763
    Jul 4, 2016 at 22:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.