Manually Adjusting Fan Speed on Lenovo L420

Platform: Debian Jessie (Testing), Linux 3.16

I have found that under considerable load such as video processing, the Lenovo L420 Thinkpad laptop gets very hot and instantly powers off.

As far as I can make out, the automatic fan speed doesn’t work as well as it should. Therefore when running under high load, it might be wise to force the fan to its highest setting. I should try and make a better fix sometime.

To manually adjust the fan speed, the thinkpad_acpi kernel module must be loaded with an extra option. Create the file /etc/modprobe.d/thinkpad_acpi.conf containing just one line:
options thinkpad_acpi fan_control=1

The fan speed can be set to maximum with the command run as root:
echo “level 7” > /proc/acpi/ibm/fan
and then reset to auto:
echo “level auto” > /proc/acpi/ibm/fan

Read the current status by using:
cat /proc/acpi/ibm/fan
Note, the reported fan speed appears to be incorrect.