The last big thing in the old parts pile is the heater box. It’s not cheap to replace, but looking at it’s condition, and I imagine the smell, I opted to go with all new. I did tear this apart 20 years ago when I replaced the heater core, and remember thinking back then that I should replace it, if that tells you anything.
There are a few major parts of the system, in 2 separate units. The bigger is the heater box and the associated plenums, motor and venting. The second is the driver side fresh air vent. I opted to get the driver side vent out of the way first as it is pretty straight forward.
In researching, I believe the original vent was metal. The one that came off my car was plastic, so I am assuming it is not original. As it was pretty dirty with a heavy coating of rust on the metal parts, I decided to also buy a replacement. Of course, I did spend some time cleaning up the original before coming to that decision. Due to how it is put together and the rubber gaskets on it, I couldn’t blast it well enough for my taste.
As with the whole system, the controls are managed by levers with cables to operate the various ducts. The driver side duct is one simple door, and the cable control is part of the unit. I did my best to take a picture to show what it looks like. The main take away here is that it’s tucked up under the dash and hard to see. Before starting the rebuild, I didn’t even know it was there. Which is impressive for something the size of a coffee can.
In the above picture, you can just see the control knob hanging down above the pedal. It will be attached to the dash where the 2 square holes are on the end towards where the steering column will be. There are 2 clip in nuts, of which one is currently missing, so I need to find them, and the 2 bolts so I can mount it correctly. As with all projects, never done with just one shipment of parts.
Next, I started on the heater box. I started with disassembling the original so I understood how it all goes together.
In disassembling it, I started with removing the clips along the seam. I seem to have about half as many on the original as I do on the new one. I also have quite a few leaf samples, and an acorn! It all came apart pretty easily.
I really wanted to salvage the original fan, but replace the motor since it’s difficult to replace later, and requires breaking the seal on the coolant system to do. Unfortunately, I just couldn’t get the fan off. You can see the little alan screw which should be holding it in place. That came off real easy, but nothing else would budge. Since the hamster wheel needs to come off to get the backing plate off, I just decided to buy the whole assembly rather than just the motor. Add that to the second round of parts for this project.
Once it is all torn down, here’s a look at the original parts. I probably could have just replaced the duct, keeping the part that connect to the dash, but with the whole system, as it pushes air, I would prefer to avoid the musty parts in the venting. Of all the parts, the plenum here is the best and could probably be re-used. Of course, its also the cheapest, so I opted to go 100% new rather than 90%.
So, from there, I took the new aluminum heater core and mounted it inside the new heater box. I opted for the aluminum version which didn’t require the end caps like the original (which mine also didn’t have, and I think I would have put them back if I had them 20 years ago). With the new box, the insulation/padding appears sufficient to keep the core from moving or rattling. It was as easy as dropping it in place and re-clipping the box together.
From there, I just had to screw the defrost duct on. The box came with the 4 screws required. It was kind of annoying to get attached as it wasn’t a perfect fit. With the help of a small flat tip screw driver, I got it in place. Unfortunately, the holes did not align. I chose the one that was seated back the furthest as my guide. After screwing that one in, I went to the drill and tapped the metal holes through the plastic as guides. After that, the holes all aligned perfectly and screwed in just fine. Who doesn’t love power tools?
The only thing left to do before the second wave of parts is to attach the ducting and control cables. I chose the ducts with some new clamp type. Not sure I like them, but I got them to work. They just have an integral cinch on the end to clamp it in place. On the plus side, they keep their form nicer than the originals.
The dash attachment is counter intuitive with how you think they would go. I climbed under the dash for a test fit to make sure I had the left on the left, etc. I highly recommend it to avoid getting additional experience attaching the venting. They went on opposite as to what I thought they would originally. Of course, I also forgot the mounting hardware for those, so that’s in the second wave of parts too. Most of the studs are there, which just clip on to the bottom of the dash, but the nuts are gone.
Finally, there’s the cables. One end is clamped together, leaving 3 loose cables on the opposite end. They are all different lengths, and it’s pretty clear how they attach based on length. Each little handle has a clamp (also included on the box). This leaves me with a box assembly with ducts and cables hanging off it. The only part missing is the blower motor and it’s ready to install in the car.
After waiting a week for the blower motor, everything went together quick. It was a little tricky getting it lined up while pushing the hoses through the firewall. The new box also didn’t line up at all for the flange that connects to the cowl. The holes are off by about an inch. I will probably just connect it with a clip rather than the bolt. I really don’t want to drill under there. It’s pretty solid for now without a fastener in that location.
It’s hard to get pictures, but everything fits like new. The defrost vents went right on perfect. I was able to reuse the clip-on screws/bolts but had to replace the nuts. Good thing I didn’t have to deal with that. It’s not in the easiest place to work in.
All of the black on black makes it hard to see, but here is the final engine side. As a note, the bolt kit on this side comes with what look like little rubber gasgets. They appear to actually be formed material closer to strip caulk. After some trial and error, I figured the best way to install it was to push the material into the cap of the nut and let the compression hold it in place. When I treated it like a washer, it all gets pressed out when I tightened the nut. Next step is to figure out the wiring.
Now that the heater box is in, I started thinking about finishing the dash again. The trim parts came in and I was excited to see how they looked. Unfortunately, CJ back-ordered the mounting hardware, so I am still waiting on that or else I could finish it and put the glove box in already. Still, looks good. I can see the light at the end of the tunnel.. for the dash anyhow.
Parts
Note: As this was a bigger project, I waited for a sale at CJ to get roughly 25% off of the things I could get there. I did a bunch of shopping around to make sure sale prices were still cheaper and the parts were the same, not lesser quality.
Brad Albrecht's Mustang Restoration Projects 