1973 Mach 1 Heater Box rebuild questions

[leener6357]

I've rebuilt the heater box in our 66 coupe and was able to find plenty of info on DIY with pictures etc, but now we have a 73 Mach1 with AC that drips condensation from the heater box into the floorboard when the AC runs. I was thinking of rebuilding the box and replacing the heater core, blower motor, etc while I'm at it but it looks totally different under there than the 66 did. I can't seem to find any info on line or in any of my manuals regarding the 71-73 system. Also, it seems that the previous owner may have tried to work around the problem with some backyard engineering. I need to see what it should look like. Does anyone out there know of a resource that would help? Pics of how it should look would really help.

 

[69 Rustang]

The basic design from 69-73 is the same. The HVAC box is separate from the blower motor and a majority of the ducting. It appears quite a bit more intimidating to remove than the simple 65-66 box especially when you consider that the 73 has integral AC. I just did my 73's a few months ago and the easiest way I found was to drop the steering column and disconnect the entire steel dash frame from the body of the car so you can pull it up and away enough to drop the HVAC. You will have to unhook the lines under the hood (of course) and, if I remember correctly there was one or two nuts that had to be removed under the hood. The rest was behind the dash. Mark your wires/vacuum lines and where they attach too as this makes it easy to put back together. The only thing I struggled with is actually getting the heater core out of the box as there is one small vent door that you cannot remove and you have to snake the heater core out around it. The other small challenges were: 1) finding all the bolts/brackets holding the steel instrument panel to the body and 2) disconnecting the speedo/instrument cluster wiring (there just wasn't much slack to pull it out enough to disconnect). You can leave the blower motor portion in the car. Test your heater core for leaks before installing it (hook it up and run the car).

Unfortunately I did not take any useful pictures, I just dove in and did it. I had it back together within a week, so the memory still grew fuzzy, but I had marked everything as I took it apart. I am getting shop manuals for my 69 for Christmas--if no one has good diagrams PM me and I will scan the pages that I think would be useful on a 73.