Control fan speed:

# echo level 0 | sudo tee /proc/acpi/ibm/fan (fan off)
# echo level 2 | sudo tee /proc/acpi/ibm/fan (low speed)
# echo level 4 | sudo tee /proc/acpi/ibm/fan (medium speed)
# echo level 7 | sudo tee /proc/acpi/ibm/fan (maximum speed)
# echo level auto | sudo tee /proc/acpi/ibm/fan (automatic - default)

/etc/thinkfan.conf

http://blog.mixu.net/2012/01/19/how-to-thinkpad_acpi-and-fan-control-on-arch/