After searching for quite a while I found out why the fan control on my Acer
Aspire One did not work any more after upgrading from 13.1:

13.2 loads both the modules "coretemp" and "acerhdf". They interfere with each
other, each one tries to control the fan accordingly, however, "coretemp" does
not do the right thing for this netbook.

To efficiently adjust fan settings "acerhdf" is the right choice, so coretemp
needs to be blacklisted on the above mentioned netbook.

Please do not say to report this upstream as my email address (not my personal
one, it is t-online.de) is blacklisted on kernel org - if anyone considers this
as an upstream topic, whoever may report it - please report.

Who wants to set thing as required, please put:
################################################
blacklist coretemp
options acerhdf verbose=0 fanon=70000 fanoff=63000 interval=15 kernelmode=1
################################################

into /etc/modprobe.d/99-local.conf. This corresponds to 70�C for fan - on and
63�C for fan - off.

Thank you for looking into this,
take care





Dieter Jurzitza