Overhauling Heater/AC Box

[charliec]

With more than a little trepidation, I decided to tackle the heater/AC box.

I took the advice of a number of people on this board, and I took MANY photos of the disassembly. What follows is a blow-by-blow of the process. First, the molded fiberglass box is old and can be brittle, which can be problematic when popping off the clips that hold the two box halves together. The fiberglass broke out on several of the locations. I was able to fix those areas with a wad of JB Weld "weld stick" pressed into place. I drilled a few small diameter holes in the parent material of the box to allow for the JB Weld to "anchor" into the parent material. After it cured, I was able to use my drimmel tool to re-shape the area and dig out a new depression for the clip to grab. I think it worked out rather well.

Once I got past the leaves, pine needles, dirt, dust and miscellaneous trash, it was obvious that the heater core was junk. That began a whole new saga.

 

[charliec]

I bought a new heater core from Layson's. While everything appeared to be a good match, I ran into trouble when I tried to install it.
The inlet/outlet tubing goes through the box through two oblong holes in the fiberglass box. Then, there is a plate that goes around the inlet/outlet tubing on the outside of the box and screws into the fiberglass box.

I got the tubing through the holes ok, but once I got the core mounting screws in place inside the box, the plate that holds the tubing in place outside the box wouldn't line up to screw it in place. If I started with the exterior plate first and then tried to install the interior mounting screws, they wouldn't line up. I couldn't line up both at the same time. I consulted with Rick at Layson's, and he advised that sometimes the tubing has to be gently tweaked to get it all to line up. That was easier said than done, as these short pieces of 1/2" tubing don't bend easily unless they're heated, and that presents additonal problems of possibly loosening a soldered joint, kinking the tubing, or burning the crap out of your hands trying to "gently" bend it.
I finally identified the source of the problem. One of the tubes, the one on the right in the photo above has a long sweeping bend befor it goes through the firewall. On the new core, that bend is very short radius. So, it goes through the fiberglass box on a different plane the companion tube. Hence, the steel plate with two pre-drilled holes in the same plane doesn't fit. You can see the long radius bend in the tube on the right in these photos.

Compare that bend with the one in the tubing that came with the new core.

 

[charliec]

I think that the easiest solution would have been to re-shape the holes in the fiberglass box and/or fabricate a new exterior mounting plate the accommodate the different tubing bends. But, did I think of that at the time??? Of course, not. I just knew that there had to be a way to make the new core work. The guy at my local radiator shop suggested sweating out the old tube and putting it into the new core in place of the one with the wrong bend radius. I liked that idea, so he went to work on it. Only AFTER everything was soldered back into place did he pressure test the assembly. Sure enough, there was a leak in the header inside the tank of the new core. Since we had already voided the warranty, we decided to open up the tank and have a look. He says that the header had a unrepairable crack in it, and that the core was junk. I have no way of knowing if the core was originally defective or it something he did caused the new core to leak. Nevertheless, I had to have yet another new core. He was able to get a new one (at about half the price I had paid ), and went to work again installing the long radius bend into the "new" new core. This time it held pressure and it looked good.
I still had the task of fitting it all back into the box and securing it. Again, the tubing went through the holes in the fiberglass box, and this time the steel plate came CLOSE to lining up. It was still going to take a little tweaking as Rick had told me. I did finally get everything lined up and secure, but not without putting a dandy kink in that one problematic tube.

At this point, I am resolved to just letting it have a kink in it, damnit!!! I will pressure test it before it gets sealed up in the box and installed in the car, but I can't imagine that that kink is going to restrict enough flow to hurt anything. Besides, it will be hidden behind the firewall.

I'll post more as I go forward.

 

[charliec]

Back to the fiberglass box...
There is a hanger that suspends the box near the passenger side kick panel. It connects to the fiberglass heater box through a hole with a screw in it. The fiberglass in that area had fatigued and cracked so that it was all jacked out of shape.

I C-clamped a piece of 1/8" steel plate to the outside surface of the box and tightened down on it to pull the surface back to as near flat as it would go.

I put a propane torch to the steel plate to help relieve the fiberglass and hoped that it would conform to the flat shape. It seems to have worked out well. Once it cooled and sat for a few days, I applied super glue to both sides of the fiberglass. So far, it has held in place. We'll have to wait and see how it does after it's re-mounted in the car.

 

[charliec]

Once I got the heater core installed (bent tube and all), I needed to test for leaks. I took a piece of 3/16 brake tubing and pushed it through a hole I drilled through a rubber stopper.

I used a second stopper to plug the other tube and immersed the whole thing in a container of water. I applied air to the open end of the tubing; no bubbles. I held the pressure for a little while till it finally popped the other stopper out of the tube, so I know it was pressurized.

I used a foam and gasket kit from DMT to finish off the re-build.

I was careful to squeeze okum into the seams between box halves as well as into every little gap I could see.

I put all the retainer clips back in place to complete the re-assembly. It looks like my JB Weld sculpture work is holding just fine.

 

[charliec]

place holder

 

[charliec]

place holder

 

[charliec]

place holder

 

[charliec]

place holder

 

[charliec]

place holder

 

[Mattax]

The current replacement cores don't fit without damaging the box.
Best bet is what you did or have it recored.

Rebuilding heater box, replace core?

So a little confused. The part number in the 63 parts book for the heater core is 2277535. Found it online, but everyone is saying it's for a 67-69 car. Plus nobody has it in stock. Classic says coming soon. 2277535 - 1967-69 Mopar A-Body - Copper/Brass Heater Core (7-3/4 This cross...

www.forabodiesonly.com

 

[superbirdrag]

Hey, theres a you tube video that is super helpfull. It make it very easy to do . I searched for ever and only found one. The guy is pretty anal which is good

 

[charliec]

On to the AC section. Disassembly was fairly straightforward, but then, it usually is easy to take things apart. The only booger was how to get this little thermostatic tube out of the evaporator coil.

It's supposed to "slide" out according to FSM, but nope! I consulted a you tube video suggested by superbirdrag on this board, and it turned out to be very helpful. I followed that guys method of cutting a slot in the sheet metal box for the tube to slide through as I pulled the coil out. I had to be careful not to nick the tube with my cut-off tool.

That allowed me to pull the evaporator coil out. I don't know of any way to bench test the switch that the coil is attached to, so I'm leaving that one to chance. The coil appears to be in fairly decent shape.

I brush blasted to sheet metal box just to get the gunk out of it and spray painted it.

I bought a gasket and foam rebuild kit from DMT which is a really nice set at a reasonable price. The guys at DMT were super helpful, even responding very quickly when I discovered that I was missing one piece out of the set. As I was getting things cleaned up to re-assemble, I THOUGHT that I was missing something else from the gasket set. There were these fiberglass insulation sheets backed with a felt paper that line the evaporator box.

I could not find them in the gasket set. I searched all the hardware stores for a substitute material that I could cut for this application, but I couldn't find anything that suited me. I finally ended up with some mastic/cork pipe wrap stuff that I used to strip line the box. It worked out OK, and I was satisfied that it would work. More on this later.

I pressure tested the evap coil the same way I did the heater core; no apparent leaks. I have no idea if there is trash in the system. I blew compressed air through it, and that's the best I can do; just have to take my chances on that count. All the guts got re-installed in the box, and I sealed up my tube removal slot with the same insulating mastic.

At this point, I stood back, took a breath, and admired my work; started picking up and cleaning up debris. That's when I found the "missing" sheets of fiberglass insulating material that were intended to line the evap box. Well, not the first dumbass thing I've ever done, and I'm sure it won't be the last. The kit from DMT was beautiful...too bad I wasn't smart enough to use the whole thing. All the panels back in place, motor painted and re-installed, vacuum diaphragms and linkages back in place. Ready to hook the AC and heater boxes back together.

By the way, there was one door inside the AC sheet metal box that gets a foam pad attached to both sides. I got one side stuck on OK, but the other side was problematic. I could barely even touch the door with my bare hands through the opening where the blower fan goes in, much less put a stickly piece of foam on the door. I got my 7 year-old grandson, Duncan, over here one afternoon, gave him some minimal instructions, gave him a couple of dry run shots at putting it in place, and the next thing you know...it's glued in. He was proud to have helped Paw Paw on the car.

 

[superbirdrag]

I found that you can buy a new thermostic tube, as long as it’s the same you can cut the old one out with out damaging the fins , tedious work I think

 

[charliec]

I found that you can buy a new thermostic tube, as long as it’s the same you can cut the old one out with out damaging the fins , tedious work I think

It would have to be tedious to say the least. I can't imagine that it's better to do that than to just buy a new evap coil complete.