i have a 1982 Mark VI just got the original R134 A/C working. blows like a champ. now i'm going to start on the heat. i can feel a little warmth coming from the vent, but obviously nothing is blowing out. the fan works, but im thinking it could be something deeper. are there any known problems for a heater core or the heater blower going out. i know the car is old. just trying to figure out where to start.