1972 Duster. Are firewalls different for heater/defroster models versus A/C ?

[Kern Dog]

I may know the answer but I wanted to check....
I have a few A body cars out back. A couple were A/C models, a couple were not.
1971 Duster Non A/C:

1972 Duster, factory A/C:

1969 Dart, factory A/C:

1973 Dart Swinger no A/C:

1970 Duster no A/C.

I see subtle differences but the most obvious ones are that A/C cars had three more holes right here:

Otherwise, the firewall stamping looks the same.
I ask this because I'd like to convert a car that came with A/C to a non A/C style while installing a basic heater/defroster setup in this car:

 

[67Dart273]

I believe so. Look up the repop firewall sections available, you can tell from the listings

 

[Kern Dog]

I know that there are more holes in the A/C firewall but otherwise, they look the same to me.
My two 1970 Chargers were original A/C models and they were noticeably different than non A/C models.
A/C has the blower motor visible in the engine bay and several holes in the firewall:

I cut that out and patched in a section from a NON A/c firewall.

Now the heater motor is hidden and there are only 2 holes for the heater hoses and to mount the heater/defroster unit.
These A bodies look like they tried to use one stamping and just punch a few more holes for A/C.

1967 Dart non A/C:

 

[Oldmanmopar]

First picture is 71 A/C second is 71 Non A'C

 

[Big.J.007]

Yes.. Here's the video guide I followed to convert my AC firewall to non ac.

 

[YY1]

Blower fan mounts differently and is a different fan.

Holes for lines.

IIRC the box for the heater core/condenser also mounts differently.

 

[Mike69cuda]

I put factory ac in my non ac 69 barracuda. There are a few mounting holes, ac hose holes, a vacuum hose hole, a drain hole, and a much bigger fan hole on an ac car.

 

[HemiSSDart]

All 67-76 A-Bodies have different firewalls for A/C vs non-A/C...

 

[Kern Dog]

Well the word different can be interpreted a few ways. Yeah, having one additional hole is enough to technically call it different so maybe to be more accurate, I needed to know just how different that they are.

I put factory ac in my non ac 69 barracuda. There are a few mounting holes, ac hose holes, a vacuum hose hole, a drain hole, and a much bigger fan hole on an ac car.

This is what I suspected but was not certain of. I can plug or weld over holes but I thought if the two designs were dramatically different, I'd find a way to weld in a different section. I was hoping that I could just put a basic heater/defroster in there and cover the unused holes. I want to sell the car with a functional heater but don't want to restore the original A/C system.

 

[HemiSSDart]

I have cut out the A/C firewall below the cowl and to the floor before, it is time consuming but it is the only way to do it right. AMD used to make each firewall section, don't think they have the A/C version now, I sold a new one earlier this year...

 

[Mike69cuda]

It was a lot of work going from non ac to ac, I haven’t tried going the other way. Should be a lot easier. The biggest issue is that the ac fan hole in the firewall is much larger than the no ac hole.

Might be easier to just leave the under hood ac stuff off and use the same heater box inside. You could leave the ac evaporator coil out too.

 

[YY1]

What's the matter with the heater core in the car now?

Seems like a lot of work to refit a different "box" rather than just put in a new core if that's what the problem is.

Is it the vacuum actuators?

If I were looking at buying a car that was factory AC and it was ripped out and modified, I'd be frustrated.
AC is important to me in humid FL.

The fan mount and some of the line holes are stamped, and as such have lips.

 

[Kern Dog]

The system is original and "seasoned". I got the car in 2007, it had been sitting with a dead slant six for at least 10-12 years. I have not tried to run power to it so I don't know if any of it works. I'm not familiar with the electro-vacuum controls and functions. The heater/defroster was simpler with a couple of cables and some simple switches.
I don't have any underhood A/C parts for this car or any other.

 

[340sFastback]

You can hook the heat/AC vacuum line to a running car and see if the switch and actuators still work. Factory service manual shows positions of actuators based on control selection. I would rebuild under dash unit with new seal kit, pressure test evaporator core, new heater core, and leave the under hood AC parts for the next owner if you don't wanna mess with them.

My guess is prob around half the potential buyers are gonna want AC.

 

[cudamark]

As mentioned, just cap the A/C evaporator fittings at the firewall and run just the heater if you don't have the A/C components for the engine. No reason to go off the deep end here. Now if all the underdash stuff is trashed, that's a different animal.

 

[Kern Dog]

I may not have mentioned but the hope was that I could restore a standard heater/defroster unit and mount it where the original A/C system was mounted.
I was hoping that the blower motor fits through the same hole, the heater hoses too. I don't mind drilling new mounting holes. I could make a cover to close off the edges of the blower motor hole in the firewall.

 

[YY1]

You can hook the heat/AC vacuum line to a running car and see if the switch and actuators still work. Factory service manual shows positions of actuators based on control selection. I would rebuild under dash unit with new seal kit, pressure test evaporator core, new heater core, and leave the under hood AC parts for the next owner if you don't wanna mess with them.

My guess is prob around half the potential buyers are gonna want AC.

Yeah, why cut your potential market in half?

 

[YY1]

Rockauto has heater cores for $42-

1972 PLYMOUTH DUSTER 5.2L 318cid V8 Heater Core | Shop Now at RockAuto

 

[YY1]

OK at least one of those is non-AC.

 

[340sFastback]

OK at least one of those is non-AC.

Heater cores for AC and non-AC are the same for the '67-'72 A Bodies.

 

[Killer6]

Stamping changed for '72 &^, looks deeper & there's a big 'eyebrow' arch between the heater hose & blower motor, not sure why. It sucks trying to enlarge an already good-sized hole in sheetmetal, I use industrial conduit knock-out shear punches, used the 4" one to make a strut-cap repair piece for the '96 GC.

 

[Kern Dog]

1967 without A/C:

1971 without A/C:

1972 WITH A/C.

I guess since the original HVAC box is dead, I need to remove it anyway. I could test fit the heater/defroster to see how things line up.

 

[340sFastback]

I guess since the original HVAC box is dead, I need to remove it anyway. I could test fit the heater/defroster to see how things line up.

Yes all the seals and insulation ect will be dry rotted and prob find leaves and debri in there. On my '69 HVAC box all the original vacuum actuators still work and my original evaporator pressured tested to 100 psi was still good. So didn't cost much to put a new seal kit and heater core in there just a bunch of labor. If you wanna go that route I can find a youtube video of a guy restoring HVAC box on '69 Dart 4 door....

 

[HemiSSDart]

To mount a heater box where the A/C box used to be you will still need to fabricate a plate for the blower motor to bolt to. If you look at the picture of the non-A/C blower motor above the four bolts mount the entire unit to the firewall which are not there if you have an A/C firewall...

 

[Kern Dog]

I’m not understanding that. The blower motors of both units look to be integrated into the whole structure of the box.