My ThinkPad W500 used to crash sometimes under heavy load because the automatic control is not speeding up the fan far enough. But I was able to disengage the fan and let it run at full speed in Ubuntu 10.10. But this does not work in my new nice and shiny Ubuntu 11.10.

Have a glimpse at fan control device.

% ls -l /proc/acpi/ibm/fan
-rw-r--r-- 1 root root 0 2012-03-18 15:46 /proc/acpi/ibm/fan
% cat /proc/acpi/ibm/fan 
status:     enabled
speed:      3056
level:      auto

Now become super user in a fresh and clean environment and send control sequence.

% exec sudo env -i bash -l
$ echo 'level disengaged' >/proc/acpi/ibm/fan 
bash: echo: write error: Invalid argument

What did I miss?

Thanks for suggests.