Just quick addition to the description.. 
Here is a log of the processor fan RPM taken over a few seconds as the PC is idle showing what I consider to be excessive changes in the CPU fan RPM whilst the CPU temperatures are quite low and the PC is idle:

Processor Fan:    382 RPM
Processor Fan:    313 RPM
Processor Fan:    328 RPM
Processor Fan:    350 RPM
Processor Fan:    386 RPM
Processor Fan:    686 RPM
Processor Fan:   1201 RPM
Processor Fan:   2105 RPM
Processor Fan:   3035 RPM
Processor Fan:   3505 RPM
Processor Fan:   3383 RPM
Processor Fan:   2775 RPM
Processor Fan:   2266 RPM
Processor Fan:   1842 RPM
Processor Fan:   1531 RPM
Processor Fan:   1305 RPM
Processor Fan:   1118 RPM
Processor Fan:    998 RPM
Processor Fan:    907 RPM
Processor Fan:    848 RPM
Processor Fan:    762 RPM
Processor Fan:    703 RPM
Processor Fan:    645 RPM
Processor Fan:    587 RPM
Processor Fan:    530 RPM
Processor Fan:    500 RPM
Processor Fan:    444 RPM
Processor Fan:    416 RPM
Processor Fan:    368 RPM
Processor Fan:    318 RPM
Processor Fan:    310 RPM
Processor Fan:    314 RPM
Processor Fan:    356 RPM
Processor Fan:    370 RPM
Processor Fan:    396 RPM
Processor Fan:    424 RPM
Processor Fan:    514 RPM
Processor Fan:    612 RPM
Processor Fan:    722 RPM
Processor Fan:    963 RPM
Processor Fan:   1330 RPM
Processor Fan:   1823 RPM
Processor Fan:   2857 RPM
Processor Fan:   3148 RPM
Processor Fan:   3022 RPM
Processor Fan:   2720 RPM
Processor Fan:   2377 RPM
Processor Fan:   1971 RPM
Processor Fan:   1670 RPM
Processor Fan:   1404 RPM
Processor Fan:    734 RPM

Here is the sensors output:
radeon-pci-0100
Adapter: PCI adapter
temp1:        +57.5°C  (crit = +120.0°C, hyst = +90.0°C)

coretemp-isa-0000
Adapter: ISA adapter
Core 0:       +31.0°C  (high = +83.0°C, crit = +99.0°C)
Core 1:       +29.0°C  (high = +83.0°C, crit = +99.0°C)
Core 2:       +31.0°C  (high = +83.0°C, crit = +99.0°C)
Core 3:       +29.0°C  (high = +83.0°C, crit = +99.0°C)

it8721-isa-0a10
Adapter: ISA adapter
in0:          +0.85 V  (min =  +1.12 V, max =  +2.28 V)  ALARM
in1:          +3.02 V  (min =  +2.87 V, max =  +0.66 V)  ALARM
in2:          +2.00 V  (min =  +2.57 V, max =  +1.45 V)  ALARM
+3.3V:        +3.29 V  (min =  +4.56 V, max =  +4.37 V)  ALARM
in4:          +2.99 V  (min =  +2.95 V, max =  +2.82 V)  ALARM
in5:          +2.22 V  (min =  +2.62 V, max =  +3.06 V)  ALARM
in6:          +2.22 V  (min =  +2.29 V, max =  +2.83 V)  ALARM
3VSB:         +3.34 V  (min =  +3.82 V, max =  +4.58 V)  ALARM
Vbat:         +3.02 V  
fan1:        1071 RPM  (min =   13 RPM)
fan2:         788 RPM  (min =   46 RPM)
temp1:        -77.0°C  (low  = +55.0°C, high = -68.0°C)  sensor = thermal diode
temp2:         -8.0°C  (low  = -58.0°C, high = -93.0°C)  sensor = thermistor
temp3:        -68.0°C  (low  = -77.0°C, high = -49.0°C)  sensor = Intel PECI
intrusion0:  ALARM

dell_smm-virtual-0
Adapter: Virtual device
Processor Fan:   1079 RPM
Motherboard Fan:  794 RPM

and a fraction of  a second later:

radeon-pci-0100
Adapter: PCI adapter
temp1:        +57.0°C  (crit = +120.0°C, hyst = +90.0°C)

coretemp-isa-0000
Adapter: ISA adapter
Core 0:       +29.0°C  (high = +83.0°C, crit = +99.0°C)
Core 1:       +28.0°C  (high = +83.0°C, crit = +99.0°C)
Core 2:       +31.0°C  (high = +83.0°C, crit = +99.0°C)
Core 3:       +28.0°C  (high = +83.0°C, crit = +99.0°C)

it8721-isa-0a10
Adapter: ISA adapter
in0:          +0.85 V  (min =  +1.12 V, max =  +2.28 V)  ALARM
in1:          +3.02 V  (min =  +2.87 V, max =  +0.66 V)  ALARM
in2:          +2.00 V  (min =  +2.57 V, max =  +1.45 V)  ALARM
+3.3V:        +3.29 V  (min =  +4.56 V, max =  +4.37 V)  ALARM
in4:          +2.99 V  (min =  +2.95 V, max =  +2.82 V)  ALARM
in5:          +2.22 V  (min =  +2.62 V, max =  +3.06 V)  ALARM
in6:          +2.22 V  (min =  +2.29 V, max =  +2.83 V)  ALARM
3VSB:         +3.34 V  (min =  +3.82 V, max =  +4.58 V)  ALARM
Vbat:         +3.02 V  
fan1:         668 RPM  (min =   13 RPM)
fan2:         788 RPM  (min =   46 RPM)
temp1:        -77.0°C  (low  = +55.0°C, high = -68.0°C)  sensor = thermal diode
temp2:         -8.0°C  (low  = -58.0°C, high = -93.0°C)  sensor = thermistor
temp3:        -69.0°C  (low  = -77.0°C, high = -49.0°C)  sensor = Intel PECI
intrusion0:  ALARM

dell_smm-virtual-0
Adapter: Virtual device
Processor Fan:    673 RPM
Motherboard Fan:  794 RPM