This article describes the steps for isolating and resolving high speed fan message alarms.

What is the cause of the "fans spinning at high speed" messages/alarms on the M, T, and/or MX routers?

If you are seeing an alarm or log showing that the fans in your router are running at high speeds, please check the following items to resolve the issue:

• Is the environment the router is in suitably cooled and circulated?
  

  The first item to check is if the rack and data center the router is located in has a cooling or air circulation system failure.   If there are other systems in the same rack or location, check to confirm if any of them are also experiencing abnormal temperatures; if so, check the cooling systems in the data center.

• Have the temperature thresholds been altered from their standard values?
  

  If the routers default temperature thresholds have been changed from their defaults to a lower setting, this could cause these alarms. You can check the current thresholds by running the following command:
  
  

  user@router> show chassis temperature-thresholds
                      Fan speed           Yellow alarm         Red alarm
Item                  Normal High        Normal Bad fan       Normal Bad fan
Chassis default         48     54           65      55          75   65
Routing Engine          55     65           90      90         100   100

  The above output shows the thresholds when the fan starts going at a higher speed, when the temperature reaches high on fan speed. If these options have been changed or lowered, they could change the range when the fans will turn on high to compensate.

• Was any new hardware recently installed or activated for the first time?
  

  If any new hardware has been put in the chassis or if any non-powered or offline hardware has been brought online when this error started occurring, you can check the current temp of the components using the show chassis environment command:
  
  

  user@router> show chassis environment
Class Item                              Status           Measurement
      Power Power Supply 0              OK
      Power Supply 1                    Absent
Temp  Intake                            OK               23 degrees C / 73 degrees F
      FPC 0                             OK               24 degrees C / 75 degrees F
      Power Supplies                    OK               25 degrees C / 77 degrees F
      CFEB Intake                       OK               26 degrees C / 78 degrees F
      CFEB Exhaust                      OK               31 degrees C / 87 degrees F
      Routing Engine                    OK               26 degrees C / 78 degrees F
      Routing Engine CPU                OK               26 degrees C / 78 degrees F
Fans  Fan 1                             OK               Spinning at normal speed
      Fan 2                             OK               Spinning at normal speed
      Fan 3                             OK               Spinning at normal speed
      Fan 4                             OK               Spinning at normal speed

  
  
  If any of the new items are showing abnormally high temperatures, there could be an issue with the component producing too much heat or a component is defective.  However, please confirm the items below and consult with the JTAC support desk to confirm.

• Are all the fans on the fan tray operational?
  

  If one or more fans in the system are nonfunctional or running at a slow/reduced rate, this will also cause the other fans to go on high speed to try to compensate for the loss of airflow.  If a fan is observed to be dead or running slow, please contact JTAC to arrange for an RMA replacement.

  
  
• Has the air filter been checked, cleaned, or replaced?
  

  The air filter is the biggest culprit for causing fan alarms going high.  The air filter for the fan tray should be removed and cleaned or replaced on a regular basis.  Juniper recommends that filters should be replaced every 6-12 months, and cleaned/cleared of dust and debris every 2-3 months. For further details on care, maintenance, and replacement of the air filters, please refer to: Maintaining the T320 Air Filters