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Discussion Starter · #1 ·
I found a large crack in the heater case on my 65' coupe today. Rather than buy a new case, has anyone tried to repair cracks in these? It's some sort of plastic but not sure exactly which kind.
 

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Use fiberglass. You may be able to make the repair from the inside to hide (most of) it.
Dave
 

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Go to Autozone, et al, and buy the small fiberglass repair kit that has some fiberglass mat in it. Take it apart, rough sand the back of the crack, lay some mat and catalysed jel, and let it set up. The gel should fill the crack from the inside. Touch up any that overflows the crack, and good as new. Good time to rebuild the unit.

Bob
 

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To repair a crack on the outside without a glass patch (changes look and texture) I used a two part epxoy product called "Liquid Steel". Blends up dark grey/black. Work it into the crack with a toothpick or similar tool and smooth. Once dry spray a rag with vinyl dye and wipe it on, makes a repair that is very hard to spot...

Doesn't show real well in the pics in this thread but the box shown had a couple cracks/gouges around the vent door face/top that were repaired as noted.

http://forums.vintage-mustang.com/showtopic.php?tid/1474471/
 

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Honestly, I had good success with Zap-A-Gap modeling glue and a "speed-up catalyst". I squirt the glue into the crack and added a drop of the catalyst and it instantly hardened it. Added a bit more, catalyst and generally built up the area I needed to repair. I had a good sized hole on the back side of the box so I filled it with a scrap of plastic that I had and then did the modeling glue/catalyst trick and it seemed to seal it just fine. No problems with the two different types of plastic, either.
 

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Discussion Starter · #8 ·
Many good suggestions. Since my first post, I found two more cracks so it looks like I have some work cut out for me. I think I'll try the fiberglass repair first since the largest crack is quite long and the mat/resin will probably be the strongest repair and I can hide it inside the case. Now I just need some fiberglass to practice on....hmmm, my neighbor has a Corvette...hehehe :)

That link from dalorzo_f is great! I did a forum search but didn't pull that one up for some reason. I am going to put in new seals, but you've almost inspired me to put in new rivets and the like. How did you clean the insulation on the fan motor wiring?
 

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Mustangerbob1 said:
Go to Autozone, et al, and buy the small fiberglass repair kit that has some fiberglass mat in it. Take it apart, rough sand the back of the crack, lay some mat and catalysed jel, and let it set up. The gel should fill the crack from the inside. Touch up any that overflows the crack, and good as new. Good time to rebuild the unit.

Bob
I've done the exact same thing to several heater boxes and a/c boxes with excellent results. The repairs are almost never seen from the outside.

I too like using the fiberglass mat. Logic I use is that if the original fiberglass was weak enough in that area to crack, I want to have a good overlap to the surrounding area to reinforce the weak spot, not just fill in the crack itself.

Don't be afraid to just jump in and do this.
 

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The insulation was cleaned with a very light quick hit of actone (paint on the wires) and then lightly wiped with either WD40 or turpentine, I don't recall which I used. After they got pretty clean a final wipe with a lanolin hand cleaner.

The wires often seem to split the insulation right at the grommet. If you are careful you can work a jewlers screwdriver inside the gromment, free the wires and pull them back inside the motor and apply a shrink wrap repair.
 

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I repaired the heater box that was in my fastback with the fiberglass mat and resin. To restore the original look, I sprayed satin clear over it and it looks just like the one in my coupe. Then, after all that work, we didn't use it. :lol:
 
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