Fan Speed on BigIP 2000 device pls help!

Hi! All

Can someone help fix high fan and noise ?

Sys BigIP 2000 with 11.6.5.3-0.0.2

Two same systems have same problems

Fan always work at maximum speed at 12K RPM (((( with no overheat and low CPU and etc temps ... 

Chassis Temperature Status
Index Lo Limit(C) Temp(degC) Hi Limit(C) Location
1 0 23 43 Main board inlet IC temperature
2 0 25 59 Main board outlet IC temperatur
3 0 32 65 Power supply #1 meas. inlet tem
4 0 34 59 Main board near power supplies

CPU Status
Index Temp(degC) Fan Speed(rpm)
1 35 11806

Hardware Version Information
Name lop
Type pic
Model F5
Parameters -- --
Boot loader version 1.04
Firmware version 4.08

Chassis Fan Status
Index Status Low Limit(rpm) Fan Speed(rpm)
1 up 1000 12000
2 up 1000 11806
3 up 1000 12200
4 up 1000 12000