Why my fan RPM drops to 0 cycling?

Question

I have installed Ubuntu Gnome 16.04 on a Dell E6430 and I am using the command

watch sensors

I can notice that, despite the temperature (around 70degrees) the fan is going max speed and after 2-3 seconds dropping to 0.

Sometimes it is stable for some time, but mostly is doing this on/off.

I tried to setup fancontrol but it doesn't seems it changed anything.

I read around forums that someone else had the same problem, blaming the hardware, the bios and so on but no real solutions.

I tried on Windows and is seems I cannot reproduce it there.

My sensors command:

dell_smm-virtual-0
Adapter: Virtual device
Processor Fan: 2972 RPM
CPU:            +62.0°C  
Ambient:        +49.0°C  
SODIMM:         +45.0°C  
GPU:            +55.0°C  

acpitz-virtual-0
Adapter: Virtual device
temp1:        +40.5°C  (crit = +107.0°C)

coretemp-isa-0000
Adapter: ISA adapter
Physical id 0:  +65.0°C  (high = +87.0°C, crit = +105.0°C)
Core 0:         +65.0°C  (high = +87.0°C, crit = +105.0°C)
Core 1:         +60.0°C  (high = +87.0°C, crit = +105.0°C)

Answer 1

What are you using to configure the fans? I've had good results with by installing i8kutils and lm-sensors, then adding the following configuration file to /etc/i8kmon.conf:

# Run as daemon, override with --daemon option
set config(daemon)      0

# Automatic fan control, override with --auto option
set config(auto)        1

# Report status on stdout, override with --verbose option
set config(verbose) 1

# Status check timeout (seconds), override with --timeout option
set config(timeout) 20

# Temperature thresholds: {fan_speeds low_ac high_ac low_batt high_batt}
set config(0)   {{-1 0}  -1  40  -1  40}
set config(1)   {{-1 1}  30  60  30  60}
set config(2)   {{-1 2}  53  128  53  128}

# For computer with 2 fans, use a variant of this instead:
# Temperature thresholds: {fan_speeds low_ac high_ac low_batt high_batt}
# set config(0) {{-1 0}  -1  52  -1  65}
# set config(1) {{-1 1}  41  66  55  75}
# set config(2) {{-1 1}  55  80  65  85}
# set config(3) {{-1 2}  70 128  75 128}

# end of file

Then you can run /usr/bin/i8kmon -d -a to start controlling the fans based on the temperature. It'll stop running on reboot, so I'd suggest adding it to your startup programs.

This has worked for me, but it's possible that you're also experiencing a hardware problem ie. a failing fan so YMMV.

Answer 2

It seems to be solved with something unexpected:

sudo service i8kmon stop

Or better (should persist after reboot)

sudo systemctl disable i8kmon.service

Probably the configuration is wrong or I don't know, but when I turned it off the fan started to behave normally, no more on/off cycles