Fan won't spin down on T420 after an Ubuntu update

[jkbkot]

I installed an update yesterday, and since then the fan on my T420 started spinning at the highest speed all the time.

I see that the two/three last updates included acpid and linux-image-generic.

I noticed this with BIOS 1.34 an upgrade to the latest 1.36 did not help. Setting options thinkpad_acpi fan_control=1 also did not help. See https://answers.launchpad.net/ubuntu/+question/182093

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: acpi (not installed)
ProcVersionSignature: Ubuntu 3.0.0-15.24-generic 3.0.13
Uname: Linux 3.0.0-15-generic x86_64
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
Date: Fri Dec 16 17:47:46 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
SourcePackage: acpi
UpgradeStatus: Upgraded to oneiric on 2011-11-05 (41 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Mathias Burén (mathias-buren)]

This affects me on 12.10 beta running 3.5.0-14-generic #15-Ubuntu SMP Thu Sep 6 23:05:06 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux.

$ sensors
acpitz-virtual-0
Adapter: Virtual device
temp1: +42.0°C (crit = +98.0°C)

thinkpad-isa-0000
Adapter: ISA adapter
fan1: 3522 RPM

coretemp-isa-0000
Adapter: ISA adapter
Physical id 0: +43.0°C (high = +86.0°C, crit = +100.0°C)
Core 0: +41.0°C (high = +86.0°C, crit = +100.0°C)
Core 1: +43.0°C (high = +86.0°C, crit = +100.0°C)