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.

Could be a clogged heater core, air trapped in the system or IIRC there may be a vacuum operated valve under the hood to not the coolant flow into the cabin area untill the heater switch has been turned on. If this vlave is on a VI, you would find it in-line with a heater hose goiing into the firewall.
My .02

need help heater not working blows only cold air been told is blend door problem on my 1988 caddy eldorao where is this at help please have kids and no heat