Fix fans running at full in Arch Linux vanilla (Kernel 3.18 and up)

So, the other day I was tinkering with a fresh Arch installation and the very first issue that I ran into was my fan was rotating at full blast even though there was now processor load at all. While looking for a solution I was surprised to find that there were no actual solutions on the internet to these. I followed the path of "Fan speed control" in Arch Linux wiki and but no luck. Then I installed 'powertop'

pacman -S powertop

Then I ran

powertop

Used Tab to navigate to the "Turntables" area. Then changed the states of all "Bad" to "Good" as many as possible. Saved using "Esc" and then reboot. It worked :)

UPDATE: Apparently this did not bring the crazy fan speeds down. After some browsing around, I hit a thread in the ArchBang forums where it became pretty apparent that recent Kernel changes in 3.18 have triggered the issue and still has not been resolved. So, I had to downgrade to 3.17.6 which I did by following a well written guide here. What I basically did was
a. Went to the Arch official package database
b. Located the Linux package
c. On the upper right Package Section of the page, click on View Changes. There I located an earlier version, in this case upgpkg: linux 3.17.6-1
d. Located the revision number from the line that is like "file:///srv/svn-packages@177020". That’s the revision number after the @, it might be anything. e. Then to compile 3.17.6, did the following in the terminal. CAUTION: This process might take several hours, took me around 4 hours to compile the kernel

cd ~/Downloads
mkdir linux-kernel && cd linux-kernel
svn checkout --depth=empty svn://svn.archlinux.org/packages
cd packages
svn update -r  linux
cd linux/trunk/
makepkg -g >> PKGBUILD
makepkg -s
sudo pacman -U *.pkg.tar.xz

This will install the new kernel. You might face some dependency issues where it might ask for 3.18. I removed those packages. Rebooted the PC and it was fixed.
Credits: https://ask.fedoraproject.org/en/question/31514/how-to-change-cpu-temperature-thresholds-and-control-fan-speed/
https://nims11.wordpress.com/2013/02/17/downgrading-packages-in-arch-linux-the-worst-case-scenario/