1973 Dodge Dart Sport No Heat.

Hi. I hear the blower motor working on both speeds. I do feel resistance when I slide the arm (I believe it's for temperature) over and it wants to slide back some. I'll check what you suggested. Thank you.

It’s not a big deal to pull the box and open it up to clean it out and verify blend door function.
I can have the whole heater unit out in about 15 minutes.
73’s don’t use vacuum controls. (Cables only)