Re: WTF did this happen:(
What probably happened is a faulty hard line in the a/c system leaking into the heater core and thus cooling the outer portion where the cabin temperature sensor is but only minutely affecting the inner portion where heat will be coming from. Might want to have that checked out, you don't want to be breathing R134a if it is indeed leaking. The section of main concern is the liquid line which is prior to a fixed orifice, after the compressor but still before the routing of lines reaches the condensor.
'06 Chrysler 300 - work in progress