Although well discussed I think more photos are helpful. These shots are from a non 1973 non A/C unit. I decided to pull the front over off the plenum to pull the heat exchanger. The important difference from other jobs is that I left the back of the plenum bolted to the firewall. The exchanger was leaking but the fan was good. As it turns out the fan was probably replaced once before. The photos show the plenum with the passenger side vent. I removed the vent, all the clips on the plenum and pulled the front cover. This exposed the heater core. I pulled the heater core by removing the screw clamps ( this heater core must have been replaced before). I cut the upper hose to release it from the nipple. For the lower hose, I tried to push it through from the underhood side but it would not come. I gave a straight pull on the heater core and it pulled out of the hose. The important thing here is that the hole in the plenum is too small in diameter to run the hose through it. If the heater core did not pull free from the heater core nipple, I probably would have pulled the back side of the plenum box. Most say that is not that much more difficult. Anyway, I removed the corroded heater core and I also removed the door assembly that redirects air inside the box. The seals are very deteriorated. I have a new set of Mustang seals from Melvin’s Ford. I plan to sand the door assembly a bit and glue on new seals.
