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1969 B-body A/C - Heater box overhaul , wanna follow along ?

Started by gtx6970, December 08, 2011, 09:52:30 AM

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This should apply to all the 1966 thru 1970 B-body A/C boxes with some small variations.
So follow along as it goes from a nasty mess to a fully operational functioning piece.

I 'll update this over a few days , there are way to many details here to do this all in one sitting.

Time wise figure approx 20-30 hours depending on your skill level and depth of how far you want to go with it.

That said, this is what you see once you have it removed from the chassis.


Now this is the type of 'blog' I'll gladly follow!  I see a sticky in its future.
Extraordinary claims require extraordinary evidence.


Ok, heres an update

They are fairly straight forward and come apart with simple hand tools and a basic knowledge.
Essentially, the box splits in 2 halves - firewall side is the Evap unit and interior side is the heater core side. Both sides are lined internally with unsulation, but said insulation is different for there respoective sides
This is what you'll find on the evaporator side .
Not much to it, just the core, some insulation along the bottom of said core. And the insulation lining the interior sides of the box. FYI, this stuff is a royal pain to remove. SO ,, again depending on the level your after, you may or may not remove it. Me personally ,  I removed most of it but saw to real need to spends hours removing every last bit. Just get most of it off and reglue your new material and call it good. It'll be fine.

This is the evap core drain tray, again just clean it out call it good.


One thing worth mentioning, The drains have 2 small ferrules that been to be removed to pull the evep drain from the box half. Go slowly to remove these, they can be tough , just not impossibile to get off the drain tubes.
I'll get a better picture later today.

once removed
And you can remove the foam seals shown here, you get new ones in the DMT kit


Once you have the outer case cleaned,and repainted.
It goes back together pretty easily.
TEST fit every single piece of of the replacement insulation before you start gluing it back in. Just in case .
I used the kit from Detroit Muscle Technologies and had zero problems but just make sure. Once it's glued down you will destroy it to remove should there be a problem.

Spray the insides of the case with weatherstriping adhesive to attach the insulation,,,,, keep in mind - a little goes a long way.
There is also a strip of insulation that gets glued to the top of the evap core. All the rest gets glued to the insides of the case.

The drain tray is attached to the evap core with two #8,  1/4" hex head screws
as both pieces go in as one unit. Make sure to replace the 2 foam seals on the tubes that seal it to the insides of the box before you put the assy down in the box half.
DO NOT put the ferrules on the drain tubes back on untill the completed box is done  and ready to go back in the car.


70 Dodge Charger 500
70 Duster (Moulin Rouge)
73 Challenger
50 Dodge Pilot House


Last one for today.
But heres an FYI,
The blend air door has a foam seals on both sides and needs to be removed to install said foam .
To remove the blend air door, just bend these tabs back that hold it in and lift straight out.You don't have to get to carried away so don't go to far and break one off.


Next up, the heter core side.
This side use a thin white styrofoam insulation. It's faily thin so handle it with care to avoid breakage.
Just spray a thin coat of adhesive to install it. Just remember, a little goes a long way so don't get to carried away with the glue. As once the cores are in place, the insulation isn't going anywhere.

The styrofoam is precut in the DMT kits. So they are pretty much fool proof, but I still suggest test fitting each pice to be sure.


Now, get your heater core ready. Be it a new one or a tested original( like this one)
New cores are avail at Classic Air if you need one. ( I had this one cleaned and flow ck, and it came back A OK )

The heater core has several foam strips to aid in sealing it inside the case. Hopefully you took several pictures when you removed it.


Make sure you replace the O-rings on the 2 tubes. I used the green  nitrile A/C o-rings
And the DMT kit comes with 2 short pieces of 5/8" heater hose and 4 clamps to replace the originals, use them.


Now that the both the core and the case is ready, Just sit it in the box.
It gets secured to the case with 2 #10 hex head screws ( circled in green )


Now, turn your attention to the actuators. Keep your fingers crossed all 3 of them are good, they are kind of tough to find NOS.
I tested all 3 and found they were all good, so I just lightly went over them with steel wool and cleared them with Eastwood diamond clear. ( good stuff btw )

The one loan removable actuator bracket was originally galvanized, so it was stripped and repainted in a paint called, bronze hammertone. I like it.


The linkages are farily complicated, so I don't suggest taking them apart unless absolutely needed. I just let them sit in solvent overnight and brushed them down with a stiff toothbrush. Then sprayed them down with WD40 and called it good.

Be sure to clean up the heater core extension tubes, These are what protrude thru the firewall and are visibile in the engine compartment side.


Sorry, I've gotten ahead of myself just a bit.

To assemble the 2 case halves. If you look along the upper edge of the ft case you will notice a rolled edge, there is also a correspending lip on the rear case half that slides into this rolled edge. Once you have the lip under the rolled edge, lower the heater side of the case half down so the 2 cases meet and are attached with 4 yellow zinc plated captives washer nuts. These are an 8-32 machine thread that thread on to studs on the ft case half. There are 2 on each end of the case. ( B - in this picture )

If you look along the bottom of the case there are a series of #10 head head screws to attch the lower lip the 2 case halves. ( A - in this picture)


Ok, now that you have the 2 cases assembled. Re-install your tested and cleaned actuators and linkages.
They look more more complicated than they are, really.

The one actuator is held to the linkages with a 3/16" spring washer clip, it can be installed after all the linkages are on( I did it this way and took some creative thinking to push it on over the stud)So, I suggest installing it before putting the linkages on the box.

My vacuum harness was still nice and flexable, so I cleaned and reused them. Now is a good time to install the heater core to firewall tube with 4 new #8 head head screws .  Hopefully once you have them all on, it looks like this.

tan top

Feel free to post any relevant picture you think we all might like to see in the threads below!

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Chargers in the background where you least expect them,97261.0.html
C500 & Daytonas & Superbirds,95432.0.html
Interesting pictures & Stuff,109484.0.html
Old Dodge dealer photos wanted,120850.0.html


Hey Bill,

Is the spring on the blend door lever the same spring that attaches to the linkage between the bottom "S" link and the case ?

Also, do you have a close up and rough tension of the linkage spring that looks similar to a distributor weight spring? My plater managed to lose mine upon getting my hardware re plated :'(

  Thanks, RJ



Quote from: 440 on December 11, 2011, 07:30:26 AM
Also, do you have a close up and rough tension of the linkage spring that looks similar to a distributor weight spring? My plater managed to lose mine upon getting my hardware re plated

This one ? I'll have to ck my spare A/C box and get you the length


Quote from: 440 on December 11, 2011, 07:30:26 AM
Hey Bill,

Is the spring on the blend door lever the same spring that attaches to the linkage between the bottom "S" link and the case ?

This one ?
This is a 1969 Charger box, and it did not have this sping anywhere else.
I have a few spare A/C boxes and ' I THINK ' the only one with this spring anywhere  else is a C-body body box. I will ck this afternoon to confirm .


Yeah Bill,
The top one is the one my plater lost....

But this is the other "missing" spring, I used your photo for reference due to the white insulation inside the box highlighting it.  Are these two springs supposed to be the same, from what I can tell they look the same.  

Last pic is the SMS box showing a spring...

I also agree this should be stickied like the grill database, lots of useful information here which will no doubt help many others.


Thanks Bill, What great timing. I just got my A/C box back from SMS and am actaully trying to install it today. They did a great job and it looks great but I am having trouble getting it mounted flush to the firewall to secure. Seems like it might be a two person operation. Is it me or are they a little tricky to get back in? Cant wait to see what comes next. :cheers:


The 1969 B-body box this is about did not have that spring. And the 67 B-body box I have on the shelf doesn't have it.


1967 has one of these, 1969 Doesn't