[CentOS] old hardware / minimal netinstall -> CPU fan control

Tue Jul 11 11:05:55 UTC 2017
Gary Stainburn <gary at ringways.co.uk>

I have just installed CentOS 6 i386 onto an old rack server (it's gonna be a 
Bacula storeage server and is a 1U 1/2 depth chassis)

I did a minimum netinstall and so far so good. However, I have one problem.  
The CPU fan is going at full speed constantly. Not a real problem apart from 
(a) it will affect the fan's lifespan and (b) it's noisy.

I've done some Googling and found some help. I've installed lm_sensors and run 


After reboot I get the following:

[root at harpo ~]# sensors
Adapter: Virtual device
temp1:       +40.0°C  (crit = +75.0°C)                  

[root at harpo ~]#

which implies that it can read the CPU temp, but the fan is still going at 
full speed.  Can anyone suggest what I need to do next to enable fan speed 

[root at harpo ~]# more /etc/sysconfig/lm_sensors 
# Generated by sensors-detect on Tue Jul 11 11:49:07 2017
# This file is sourced by /etc/init.d/lm_sensors and defines the modules to
# be loaded/unloaded.
# The format of this file is a shell script that simply defines variables:
# HWMON_MODULES for hardware monitoring driver modules, and optionally
# BUS_MODULES for any required bus driver module (for example for I2C or SPI).


# For compatibility reasons, modules are also listed individually as variables
#    MODULE_0, MODULE_1, MODULE_2, etc.
# You should use BUS_MODULES and HWMON_MODULES instead if possible.

[root at harpo ~]#