Comment 12 for bug 410596

I had the exact same behaviour on a Dell Latitude E7440.

I managed to get the workaround working (compiling smm from the i8k source, calling it to disable BIOS fan control which was fighting with the fan speed set by i8k).

Here's what I did:

Downloaded the i8k source:
$ apt-get source i8kutils

Installed some packages I needed for the compilation:
$ sudo apt-get build-dep i8kutils

Compiled with the -m32 option since I'm on a 64-bit system:
$ gcc -g -O2 -Wall -I. -o smm -m32 smm.c

Ran smm with the suggested command to disable BIOS fan control:
$ sudo ./smm 30a3

After that, nothing is fighting the fan speed I'm setting with i8k. Works perfectly.

(Just too bad that you can only set off and two fixed fan speeds. I believe however Dell is to blame for that.)