I scoured LOST for a good how-to on replacing the KK's blower motor and blower motor resistor, and came up empty. There is a very well illustrated how-to on Jeepforum, though. Rather than reinvent the wheel, here is the thread by lsejlowe on JF:
http://www.jeepforum.com/forum/f292/08-liberty-blower-motor-replacement-how-1517528/How to know which is causing your problem:
It's the blower motor if the fan isn't spinning at all or makes a grinding/screeching sound.
It's the blower motor resistor if not all your fan speeds work (typically only blows on high).
I replaced the blower motor in my '08 this year. The bearings went bad, so it sounded like a helicopter taking off.
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2008 Liberty Sport 4x4 Automatic
Jeepin By Al 4" Lift Kit
BFG KO2’s 245/75R16
Full MOPAR skid plates
Rock Lizard Skink Super Sliders
AtTheHelm Front Recovery System & Roof RackM116A3 Trailer build thread: viewtopic.php?f=72&t=77997