Heater box, rebuild or replace?

[Mark Jones]

Has anyone done a rebuild on their heater box? With the engine at the machine shop, I have started on the interior. I removed the heater box this weekend. I found a broken piece at the side of the box which could be repaired. Of course all the foam is shot, and the flappers are rusted (which can be corrected) I dont know if the heater core is good but I am leaning toward replacing it.
I just wonder if it will be worth rebuilding the original box. Repo boxes are available but the prices are all over the map. Are any one of them better than the other or would I go for the lowest price. Any suggestions??
- Do I take the heater core to a radiator shop and have it pressure tested and repaired if needed or do I just buy a new core
- If I replace the heater box, I still have to use all my old hardware and vacuum motors. Is it really worth it.
- Does the A/C core need to be replaced?? How would I know. Is the 72 OEM core R134 compatible?
I haven't tested the fan yet but the squirrel cage seems to rotate easily.

 

[Sheriff41]

Others on here have said the replacement boxes are better quality than the original ones. Not sure which brand is best but from the pictures on the various suppliers' web pages they may all come from the same source. If yours is repairable and otherwise in good condition then that would be the way to go, IMHO. Cracks can be repaired with fiberglass and you can get a seal kit from most all the Mustang suppliers.

Definetly replace the heater core with a new one while you are there. They're not expensive and you don't want to have to replace it a year or two down the road.

The A/C evaporator is probably good and shouldn't need replacing. The core is compatible with R134 but you will need to run different o-rings and R134 compatible oil. If you still have the York piston compressor you may want to change to the rotary style compressor. The rotary is a lighter weight and efficient alternative that you see with most retrofit kits and on modern applications.

 

[BUCKWHEAT]

Has anyone done a rebuild on their heater box? With the engine at the machine shop, I have started on the interior. I removed the heater box this weekend. I found a broken piece at the side of the box which could be repaired. Of course all the foam is shot, and the flappers are rusted (which can be corrected) I dont know if the heater core is good but I am leaning toward replacing it.
I just wonder if it will be worth rebuilding the original box. Repo boxes are available but the prices are all over the map. Are any one of them better than the other or would I go for the lowest price. Any suggestions??
- Do I take the heater core to a radiator shop and have it pressure tested and repaired if needed or do I just buy a new core
- If I replace the heater box, I still have to use all my old hardware and vacuum motors. Is it really worth it.
- Does the A/C core need to be replaced?? How would I know. Is the 72 OEM core R134 compatible?
I haven't tested the fan yet but the squirrel cage seems to rotate easily.

1. Heater core: buy new one, but only after your box is out. On mine, the new core is high quality but fits too snug for door to work. Do a dry run assembly to be sure the doors work easily.
2. Old parts: they should be ok. Check mechanical and vacuum action. Likely best to get new hoses.
3. A/C core: I did not replace mine, and system took a recharge just fine. But my control needs help. Compressor runs fine on direct power but not thru dash switch.
4. Fan cage and motor. I am not getting air flow in the right places because doors don't work. I bought a new fan and kept the old one . Someone posted here that new fans are not as good as originals. I will check both.
5. R134: My mechanic says not to worry about compatibility.
Mark, all this is my opinion. I basically am doing the whole HVAC job twice just to get it right. Be patient and persistent.

 

[Mark Jones]

Others on here have said the replacement boxes are better quality than the original ones. Not sure which brand is best but from the pictures on the various suppliers' web pages they may all come from the same source. If yours is repairable and otherwise in good condition then that would be the way to go, IMHO. Cracks can be repaired with fiberglass and you can get a seal kit from most all the Mustang suppliers.

Definetly replace the heater core with a new one while you are there. They're not expensive and you don't want to have to replace it a year or two down the road.

The A/C evaporator is probably good and shouldn't need replacing. The core is compatible with R134 but you will need to run different o-rings and R134 compatible oil. If you still have the York piston compressor you may want to change to the rotary style compressor. The rotary is a lighter weight and efficient alternative that you see with most retrofit kits and on modern applications.

Thanks for the advice. I am with you on the heater core. I dont want to have to do this again. Other than the broken part, the rest of the box is in decent shape. I may just buy a re-seal kit and call it a day. $350 will buy a lot of other misc parts I need for other things.

 

[Cleveland Crush]

As others have stated-with out a doubt, get a new heater core (along with new foam insulators)

 

[73CobraJet]

Be careful with the new heater cores! The ones I bought were Chinese junk cuz nuttin made here anymore. Bought two and they leaked on my fellettes new shoes within a mile! Took a guy forever to get in Mustang and that’s what happened!

 

[JDuvall]

I rebuilt mine with the factory style replacement shell. I would do it differently now, I would go with a vintage air or a classic air unit. Theses units are all electric and are made for modern refrigerants. With the factory style I uses a new heater core but did not replace the vacuum servos. I was over half the cost of just replacing the whole factory unit with the vintage air. Just my opinion.

 

[Paul M]

I ran through mine last month. I fully disassembled it, cleaned it and reassembled it. It probably wouldn't have worked very good with the crap I found inside it. You have to have the dash moveable to remove it. I also removed the blower motor and disassembled it. I used a lil light oil to free up the grease inside the sealed bearing a bit & the blower motor tested good and strong w/out excessive side play, so I reused it. When I was fully reassembled the blower motor still wouldn't work. I had to replace the resistor concoction on the side of the blower box. I reused the heater core since it didn't show any signs of leaks & looked acceptable on the inside. of course, everything was removed and cleaned. Yes, I had a cpl of small repairs, not a problem and the flimsy fasteners on the rods that hold the doors are fragile. I ended up safety wiring one for extra security.

 

[Hemikiller]

I had a parts store core in my '71 that finally failed after 15 years. Replaced it with an aluminum from the same parts tore and it failed within six months. NPD sells a copper/brass unit that is very high quality. It's not cheap, but you get what you pay for here.

https://www.npdlink.com/product/hea...%2Bcore&top_parent=200001&year=1973&year=1973

 

[dawson357]

Just finished rebuilding mine. I too had a chunk broken off the case but was able to make a solid repair with JB plastic weld. Also repaired one of the holes that a flapper rod went through with JB Weld and epoxied on a metal washer as extra support. Replaced the heater core and evaporator with copper and brass ones from Classic Air. A few extra bucks but I figured that while I've got it out (and it was a pain to get out) I might as well go ahead and bite the bullet. All the vacuum units worked fine and blower just needed a cleaning and new foam. Haven't hooked up the system yet as I'm in the process of swapping out the FMX for a top loader which requires removing the headers. Easier to get to them without the heater hoses and such in place. Hope it all works when the day comes to fire it up.