cpu fan speed freezes

[Jesse Geens]

cpu fan speed always freezes at 525RPM

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: udev 204-5ubuntu20.24
ProcVersionSignature: Ubuntu 3.13.0-24.47-generic 3.13.9
Uname: Linux 3.13.0-24-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.25
Architecture: amd64
CurrentDesktop: X-Cinnamon
Date: Mon Oct 23 22:24:18 2017
InstallationDate: Installed on 2015-08-06 (809 days ago)
InstallationMedia: Linux Mint 17 "Qiana" - Release amd64 20140530
Lsusb:
 Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
 Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
 Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: LENOVO 2550W1E
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=nl_BE.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-24-generic root=UUID=81f09e4c-e8db-48d1-9083-0ef6bfbec68f ro quiet splash vt.handoff=7
SourcePackage: systemd
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 12/10/2010
dmi.bios.vendor: LENOVO
dmi.bios.version: 81ET48WW (1.24 )
dmi.board.name: 2550W1E
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr81ET48WW(1.24):bd12/10/2010:svnLENOVO:pn2550W1E:pvrThinkPadL512:rvnLENOVO:rn2550W1E:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 2550W1E
dmi.product.version: ThinkPad L512
dmi.sys.vendor: LENOVO