AC/Heater Box R&R in a 74 Dart

[Acuda4me]

My new to me 74 dart came with the patented "redneck heater core bypass" installed under the hood, so I'm pretty sure my heater core needs replacing. To make matters worse, this car once suffered a clogged cowl drain flood so severe that all of the gauges had to be replaced. Has anyone done a heater box R&R on a factory AC car enough times to give me a step by step? (Or point me to one online) Do I have to depressurize the A/C system? (Assuming it still has any pressure.) Also, the fan switch is inoperative (I suspect another victim of the flooding) I think my best course of action is probably to remove and rebuild the AC/Heater box so that i can inspect all of the components/electronics. Any thoughts?

 

[Warren]

Yes, you will need to depressurize the A/C system and then disconnect the 2 aluminum tubing fittings for the evaporator on the firewall in the engine compartment. You will need to remove the A/C outlet vents assembly (2 screws on the bottom). You will need to remove the glovebox liner to access some evaporator bolts, wiring, and vacuum tubes. You will need to remove the passenger kickpanel and the lagging screw which bolts the right side lower dash to the body (will allow some flexibility when lowering the evaporator box.) According to the shop manual, which I advise obtaining, you will then remove the radio and ashtray assembly to access some more screws to then get the heater box out (I have not had to do this on my heater core as is ok, 1974 Dart Sport.)