73 Heater Box + Core Removal 1-2-3

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rocket366

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73 With AC

Removed my heater box today for heater core replacement and sharing step by step.

Disconnect battery.

Evacuate and disconnect AC lines under hood.

Disconnect heater hoses under hood.

Remove two heater box nuts at firewall under hood.

Inside car

Remove passenger seat.

Remove passenger kick panel.

Remove glove box and door.

Remove left Vacuum pot from box and mark hoses.

Remove temperature cable from heater box.

Remove two AC thermostat wires green front black rear and mark wires.

Remove vacuum line from right side box vacuum pot and mark hose.

Remove box to cowl bolt.

Box now free to remove from car.

On Bench

Remove spring clips that hold two box halves together by spreading

the clips with a large flat blade screwdriver... do not pry clips off as

may cause damage to fragile fiberglass box.

After box halves are separated the main temp control rod and flapper have

to be removed to get to the heater core and this is tricky because the rod has to be pulled out of the flapper and it is rusted together. Soak and let

sit with penetrating oil while having a few beers is best. After some twisting

and getting it loose the rod will pull straight out as it is flat spotted in two places so it just doesn't spin on the flapper. That is the hardest part of the

tear down.

There are 3 control levers on the box and their function is...

Center Top Lever: Move Left = Fresh Air From Cowl + AC, Move Right = Heat + Hit Switch

Center Bottom Lever = Move Left = AC, Move Right = Fresh Air + Heat

Right Lever Move up = Fresh Air From Cowl, Move Down = Recirculate Air

It takes some thinking to understand the door flapper functions and how they work together to do the climate control thing.

Anyway it took only 1 hour to drop the heater box after the hoses were disconnected.

It took me about 4 hrs to disassemble the heater box and clean it up

for reassemble.

The flappers have foam insulation on them to seal when they close that

will be rotten and is reproduced,

Couple photos.

ofyjxi.jpg


You Never know what surprises you will find like A RATS NEST!

34fem38.jpg


Regards

Paul

 

Manu Mach1

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I removed as well the carpet from the passenger side, it helped me a lot cause not a lot of room in this area when this job needs to be done.

Good thread for the ones who need to remove the heater box...

 

MotoArts

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Thank you for the writeup. A timely one at that, as I will be converting a non-AC to an AC car shortly.

 

1973_Mustang_Conv

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Thank you for the writeup. A timely one at that, as I will be converting a non-AC to an AC car shortly.
Pete,

Did you convert your car to AC ? Did you use NOS parts?

I am looking at using NOS parts (Compressor, Evaporator, Condensor) that the PO provided me and would like any pointers .

 

lduke12

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So Rocket366, you didn't have to remove anything else from the dash to remove the A/C Heater box, that whole thing came out from under the dash? Or did you have to remove the whole dash itself to get it out?

 
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So Rocket366, you didn't have to remove anything else from the dash to remove the A/C Heater box, that whole thing came out from under the dash? Or did you have to remove the whole dash itself to get it out?
I was able to remove mine without having to remove the dash. With the seats and center console removed there was enough room to get it out.

 

rocket366

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I actually left the passenger seat in and after everything was unbolted

and disconnected it fell out no problem.

I should have taken the passenger seat out as my back reminds me!

 
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One critical area that I did not see mentioned, is the evaporate tube through the floor pan. I have seen many of the extension tip of the box damaged due to not being careful when removing the box. Just my 2cents!

mustang7173


1973_Mustang_Conv,

Does your mustang have just heat/air or have factory installed A/C?

mustang7173

 
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I am pulling a complete AC system out of a 72 vert when it quits raining here if anyone interested. What do they go for?

I also have some parts and pieces probably not going to add the air to my 72 Q just too much stuff.

David

 

Justin71

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It's funny, removing the seats are just 4 nuts under the car. For some reason it seems like a big deal, but it's really easy to do, and MAN, it leaves you a lot of room to work! (besides - you need to clean under there anyway!)



One critical area that I did not see mentioned, is the evaporate tube through the floor pan. I have seen many of the extension tip of the box damaged due to not being careful when removing the box. Just my 2cents!

mustang7173
That's a GREAT point. The old fiberglass on these original boxes is very brittle, and the nipple it is mounted on will break easily. The best thing to do is CUT that hose off just inside the car, and replace it with a new supple hose. I installed the hose by coming up thru the floor after the box was put back in place, and it wasn't perfectly aligned and I still had to be careful.

And that point reminds me, the OTHER place that likes to break easily is the mount bolt that goes thru the firewall on lower left (on AC cars) I would remove the nut from this bolt completely before loosening the rest of the box up. Then, you need to carefully pull the box away from the firewall so this stud doesn't hang on the wall and get so much bending on it that it breaks the case where it is mounted. Mine was very difficult to patch - I had to form some sheet metal around the odd shaped corner, and hold in place with JB weld and pop-rivets. (not pretty, but nice and strong)

 
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rocket366

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CMM

If you get rid of the system entirely you will not have

defrost capabilities and from experience its no fun early

mornings or after dark.

 

1973_Mustang_Conv

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One critical area that I did not see mentioned, is the evaporate tube through the floor pan. I have seen many of the extension tip of the box damaged due to not being careful when removing the box. Just my 2cents!

mustang7173


1973_Mustang_Conv,

Does your mustang have just heat/air or have factory installed A/C?

mustang7173
All I have currently is a leaking heaterbox. The previous owner supplied me with NOS Air conditioning parts. So I have the compressor/Condensor/Evaporator (all which I will need to test/check) . So to answer your question, orginally heat/air no A/C yet and knowing the Carolinas I'll need it soon.

 

mrmach1

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It's funny, removing the seats are just 4 nuts under the car. For some reason it seems like a big deal, but it's really easy to do, and MAN, it leaves you a lot of room to work! (besides - you need to clean under there anyway!)



One critical area that I did not see mentioned, is the evaporate tube through the floor pan. I have seen many of the extension tip of the box damaged due to not being careful when removing the box. Just my 2cents!

mustang7173
That's a GREAT point. The old fiberglass on these original boxes is very brittle, and the nipple it is mounted on will break easily. The best thing to do is CUT that hose off just inside the car, and replace it with a new supple hose. I installed the hose by coming up thru the floor after the box was put back in place, and it wasn't perfectly aligned and I still had to be careful.

And that point reminds me, the OTHER place that likes to break easily is the mount bolt that goes thru the firewall on lower left (on AC cars) I would remove the nut from this bolt completely before loosening the rest of the box up. Then, you need to carefully pull the box away from the firewall so this stud doesn't hang on the wall and get so much bending on it that it breaks the case where it is mounted. Mine was very difficult to patch - I had to form some sheet metal around the odd shaped corner, and hold in place with JB weld and pop-rivets. (not pretty, but nice and strong)
Not to go off subject but my seats unbolt from inside the car. Are your's different?
 
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Justin71

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It's funny, removing the seats are just 4 nuts under the car. For some reason it seems like a big deal, but it's really easy to do, and MAN, it leaves you a lot of room to work! (besides - you need to clean under there anyway!)



One critical area that I did not see mentioned, is the evaporate tube through the floor pan. I have seen many of the extension tip of the box damaged due to not being careful when removing the box. Just my 2cents!

mustang7173
That's a GREAT point. The old fiberglass on these original boxes is very brittle, and the nipple it is mounted on will break easily. The best thing to do is CUT that hose off just inside the car, and replace it with a new supple hose. I installed the hose by coming up thru the floor after the box was put back in place, and it wasn't perfectly aligned and I still had to be careful.

And that point reminds me, the OTHER place that likes to break easily is the mount bolt that goes thru the firewall on lower left (on AC cars) I would remove the nut from this bolt completely before loosening the rest of the box up. Then, you need to carefully pull the box away from the firewall so this stud doesn't hang on the wall and get so much bending on it that it breaks the case where it is mounted. Mine was very difficult to patch - I had to form some sheet metal around the odd shaped corner, and hold in place with JB weld and pop-rivets. (not pretty, but nice and strong)
Not to go off subject but my seats unbolt from inside the car. Are your's different?
Sorry. I have most experience with my 69. The 69 DOES unbolt from under the car, and I have not take the seats out of the 71. Now that you mention it, I know the rails are different between the 2 cars, and the mounting on the 71 probably is inside.

Jay

 
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I received my new heater core today and ordered a copper one. I have one rule I have not seen in this discussion on heaters. I always pressure test the new core before installing. I changed one in an econoline van once and got it all together and took it out and the new core leaked. That vehicle you have to pull the whole dash out.

So I took the new core outside put in a bucket of water and put 15 lbs. air pressure and D*&% there came the bubbles. There is a hole in the tubes somewhere in the brand new core.

I suggest that you always test these things or you might be tearing it apart again. That is two for me and I have probably not replaced but maybe a dozen in my life.

I bought it off ebay now to get my money back and I will just go local this time been waiting nearly a week and half for this one.

While waiting I went ahead and took the entire dash out and have refurbished everything and ordered the sound insulator for the cowl. I am going to install a piece of 1/4" mess wire between the cowl and the intake on the heater core to keep anything out. I only have a few leaves and pine needles but if your car sits in a garage you will have critters in there. I am also going to put the mesh wire under the two plastic grill on the cowl. They can still get in through the water drains on the sides of the cowl but not as easy. I had a black snake get in one of my cars I was sitting in it and here it comes out from under the dash. That will get the heart going don't care what kind of snake it is.

TEST THE CORE.

David

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