Lady72nRob71

For the longest time I never knew what held the top of the chunky dash vent distribution plenum to the heater box. The bottom has two screws, which the holes can be seen here…


I never saw how the top was held and this was a big source of rattles when driving on rough roads.
So I did a trial fit to see how I could get it secured. The answer jumped out and hit me as soon as I put the pieces together - this long metal clip!


Originally, this clip was bent way back and the temperature door cable was running under it, so I thought that was its purpose!!
Luckily I was wrong. I bent the clip to where it would securely hold the top of the plenum. There was originally a thin foam gasket that went in between, but I think I will use a thin bead of the strip caulk.
Mystery solved!

While thinking of strip caulk, I worked some in between the joints of the center air duct to prevent rattles. I think it will work fine.


While I was under the dash, I added a wire to the alarm module to operate my new trunk release. Also, while the kick panel and sill plate were off, another set of RCA patch cables were run form the radio to the amp under the seat. I will need those later when I get a new radio.

Okay, I think the box can go back in the car now!

Allan R

I hate rattles too.
HOLY SPAGHETTI FACTORY BATMAN!! That's a real maze of wires you have running there. Hope I can keep mine looking more simple when I install the courtesy lighting package.

Nice write up. Makes me wish I had AC in my car

Lady72nRob71

90% of those wires are from that aftermarket radio, most which are unused.
That big blue one is the factory rear speaker lead, which will now be used to power the trunk release.
The orange and white to the left are for the glove box light.
NOTE TO SELF - see whats under the tape on the orange....

Would you need A/C in Canada? I figured there would be only a handful of days per year over 90!

Allan R

Yeah, the aftermarket system in my car looks just as bad. I'm going to yank it all out and put in an OEM AM/FM Stereo / 8 track. I have all the proper wiring and diagrams. + Randy (w70442) if I run into trouble.

Why would you use the blue wire to power the trunk release??? Theres a jumper assembly from the glovebox light to the power trunk release. You can get them repopped from ILT http://www.ebay.com/itm/1970-71-72-o...item5acf07be26 $14.00


reference 72 Assembly Manual page 12-120. Why make life more challenging than it needs to be??

AC in Canada? We don't need no stinking AC.... Days over 90?? Heck try days over 75... I can always dress for cold weather. How much can you take off in 90+ weather without getting arrested? I HATE hot weather. It's so hard on the dome of my igloo . Can't sleep at night when it's hot.

Lady72nRob71

Lady never had power trunk release and I do not feel like buying a harness or installing the button. The alarm remote will pop it for me; justy need one wire to do it. The blue wire is now unused, so might as well use it for something - it was right there. This is one of the rare GOOD MAWs...

Allan R

Sounds like I have to come down there with my stick. Well on the other hand, you have electrically heated seats that never came with Lady either. She's got old and new world tech. Never really understood why verts came with AC or door locks

I'll go ahead and do my power trunk the old fashioned way. I think it will be a new thread with the usual pics and write ups.

2blu442

Wow! I've been too busy to comment on this thread Rob but as always, you've done a really nice job documenting the project. Next time someone asks "how do I change the heater core?" all we need to do is point them to this thread

John

O's_Car

Below are the pics I have of the defroster door. Nothing fancy, I just removed the staples, cleaned off the old foam and adhesive, and stuck on a new piece of foam that was included in the seal kit. I didn't re-use the staples, they were incredibly stiff (given their use here) and I didn't want to bother with them again. I just made sure the foam was completely attached with weatherstrip adhesive. As it turns out the return spring was broken and the door wouldn't close, so I replaced that as well.

Now don't be giving me grief about my nifty designer table cloth - it's a $5 piece that kept the weatherstrip adhesive (and other gunk) off my kitchen table!

Miles71

Hi Rob:

In picture 3497.jpg Center Dash AC vent, did you have a self-tapping screw joining the two sections together? If so, any ideas on how to get that screw back in?

I had to remove the center vent to get my old 4x10 speaker out (still need a working replacement). My center vent had a screw on the top (speaker side) joining the two sections. I was able to remove the screw with a small thin wrench, reaching in the blind over the top of the vent.

However, trying to align up the two vent sections perfectly to get the old holes to align and then fit the screw back in have been too difficult for my hands. Maybe ill just dill a new hole on the Radio side of the vent and put the crew in from the accessible bottom?

I like the idea of Caulk. One of my vent parts vibrates on Medium and High fan settings.

Lady72nRob71

Well come on down and get me! You will have to travel into Dallas in the SNOW. I am sure sheer panic is setting in at most gas stations and stores. Even though they are just flurries...

Thnaks - that's the plan! I've been through it and lived to tell about it, so you can too!

Nice detail work on the door. I do not think I will mess with mine. Rarely need a heater anyway.

The assy manual states there is a plastic peg that holds the two sections together. I never saw a screw but I will try to peek up there tomorrow.

This should work well. It will still move to align up but is sticky enough to not rattle...

Lady72nRob71

So on a mid February day in the mid 70’s, I got the heater box back into the car. Nice to have the floorspace back in the kitchen before I lost a toenail on the heater.

Installing is pretty straightforward, but I have some recommendations.

First, like during disassembly, covering the carpet with tough plastic is vital, whether in a daily driver or a show car. In the end, the strip caulk that had squeezed out of the bottom of the case made a nice mess on the plastic. If this had been the carpet……………
Next, have your fasteners and tools ready nearby. Also a couple blocks of wood to support the unit as needed.
You might need a helper. If the heater core pipes are not spaced just right to go through the firewall holes on their own, someone will need to help coax them from the outside with wooden dowels. Also, he or she can put on the nuts on the firewall side as the studs poke through. This prevents the box from falling off when you get tired and try to rest.

It is easiest to keep the box up right, slide it under the dash carefully and when the temp door mechanism is under the dash, start shoving the unit to the left to clear the recirculate door.
It will take some effort to get it up just right to get the studs and pipes all lined up and through the firewall. Take care not to tear up the firewall mat or break the recirculate door actuator!

At this time I was unfortunate to have all of my helpful neighbors away so I had to do this myself. I tried to get the pipes through first, while holding the unit up with my left foot and knee. Never thought I would be twisting myself up in yoga positions to do this! Having a bench seat made this easier. You guys with consoles will have even more fun!
The pipes of the core were too close to each other but out of desperation, I painfully wedged my finger between the pipes and pushed and the right side of the unit popped somewhat into place. I supported it with blocks and hoped it stayed!
From the outside I threaded on one nut by the pipes. The rest of the studs were almost through.
I finagled it some more and it popped into place more. I supported it again with blocks.
Again, from the outside, I threaded on two more nuts loosely.
From the inside I gave it a final push and it went in all the way. I was now able to get the two inside bolts on with no issue. I snugged them some then snugged up the outside three some. I repeated this again until they seemed tight enough. Do not overtighten! I will do that fourth nut from under the car sometime later.
During this install I kept thinking of Bluevista’s observation that “even a blind squirrel finds a nut now and then”. Half of the fasterners had to be installed by feel. Therefore, even blind Rob gets a screw or nut on after a while of fiddling!

So now it is in.
Here is where I forgot to attach the temp door cable! However, it was easy enough to attach afterwards. During the heater box installation, I had wired that cable to the radio shaft to keep it out of the way.
I adjusted the cable at the turnbuckle to give the temp lever the 1/8” of springback at both extremes.

Next the defrost duct and adapter were installed. These could have been installed prior to the HB, but either way is okay! It could have been in the way if it was installed first…
Make sure the rear clips for the defrost adapter go into the louvered slots to hold it, then install the front screw.
The heater vent was installed, the hose connections, the kick panel, and the sillplate.
The A/C vent plenum was last. Make sure the top goes under the top clip and the top nozzle goes into the center vent duct. I found that the center duct nozzle had too much gap in it so I fixed that with some foam weatherstrip.
Rest of the vents were connected and lastly, the lower dash valiance and crotch-cooler vents.

The heater core pipes will be connected and the job will be done!
(Hopefully)…
I found that after this renovation that all of these parts now feel tighter and more secure than before. Hopefully this will mean less air leaks and less rattles!

Allan R

On my way down to rescue you lil buddy! Snow is no big deal. Up here the panic sets in when there's dry pavement and warm weather . That's when people start driving really stupid!

BTW, don't know if you noticed, but the pics in your "out of the kitchen' post didn't come through. So unlike you..... I like your write ups, especially how the pics illustrate the text. From the read through, it was obvious that you intended them to be there....? glitch???

oju392

This bracket fell out of the box when I removed the heater core from my 72 Cutlass S anyone know where it goes? I cannot figure out from any pictures or drawings where it came from.

Lady72nRob71

I looked all over my pictures of that box and could not find it.
You are not the only one to have asked about that part, too. I kinda remember it from my own box, too. I kinda also thought I look it off and left it off for increased air flow through the dash vents...........

oju392

Thanks, I am totally puzled where this bracket went and I will leave it out as I don't think it would be very helpful with it not having anything I could find that it would align with. I will also leave it out.
Thanks for the help!

jensenracing77

Great thread Rob.

Allan, I have 3 1970 under dash A/C heater boxes that do not have it. I have 2 1972 units that do have it. Not sure when they made the change. The boxes without it are a little differant color than the ones that have it.

Waterworld

The bracket is located inside of the heater box and attached via two screws located on the outside of the box.
photo 3.JPG

photo 2.JPG

photo 1.JPG

MDchanic

Welcome to ClassicOlds, and with a helpful first post, no less!

- Eric

Waterworld

Thank you Eric! This thread was invaluable while replacing my heater core recently and it is nice to give back.

I'm sure many other threads this forum will help with the many other projects I have to get my girl back on the road!

Waterworld

This is a great tip! The clip on my box was too loose and would have rattled as well. I used some dense foam speaker gasket instead of caulk to seal the surfaces, and added some felt tape to the upper lip where the metal clip and plastic meet. Since the foam seal may not stop the two surfaces from moving relative to one another (unlike using the 3M caulk), I thought this might prevent possible squeaks from side-to-side movement. It is probably not needed, but I had the felt tape laying around and thought "why not?!"

Lady72nRob71

Thanks!
That is interesting that it was added later. I wonder what 'purpose' it had?
I found it just blocked some airflow to the dash vents...

Welcome to the site and thanks for shedding the light of where this thing went. Out of all the pics I took of the box, I never had one showing the part's location.
BTW, Waterworld was a pretty cool movie, despite that the 'critics' said otherwise. I had dug out the VHS of it a couple years ago and really enjoyed it. So much more real looking than computer generated stuff now days.

Glad I could help out!

oldsguybry

X2 on the Waterworld movie .

glide65

Really enjoyed the thread. Just finished doing mine in October. This article would have made it much easier................. Mr. Young, you are a credit to this forum.

White_Knuckles

^ indeed! A Jedi documentation master.

Always quality photos with descriptive descriptions rather than mysterious, ambiguous statements.

We know the time it takes to edit and post this stuff. Maybe a "bound" edition - a series of your work PDF-ed and sold on the forum? It'd be a hit for an owner restoring one.

I do see the benefit of recording and narrating video in an assembly process where you see the whole deal. However, if the guy doing the work is speaking, often they start rambling never mentioning tips or tricks. If I ever make one of those things, I'll consider things to NOT say.

Lady72nRob71

Thank you very much...
I am always happy to help where I can.
Glad it can help others to keep their old cars going and not make any of the same blunders that I did!

Lady72nRob71

Thank you, too!
I thought about and actually started on a PDF edition, but I never had the time to get it very far. While it was going to be for myself only, publishing is an idea.........
A live video would be bad, as it would be full of all the stuff of what NOT to do. Now I could sell the bloopers and live off the income - think Bill Dance...

jensenracing77

Rob, I was talking about the molded spot that looks like a bolt in the fiberglass.

White_Knuckles

^ Yeah, I studied that shot wondering if a bolt fell onto wet paint or glass leaving the impression? The threads extend all the way up to the bolt head which didn't make sense from a drop. I figured it was one of those "ghost" deals where the photo produced this anomaly that may only be solved by a TV paranormal team.

hobgoblin2

Just want to say "thanks" in advance. I'll be replacing the heater core on my 69 shortly. This will be most helpful. I wonder why GM didn't have the intelligence to make a door on the inside of that heater box to remove the core. May check into doing that while it's out. lol

GeneralWAS

Nice job and thanks for all the insight into replacing the heater core I just have one question.
What did you do about the clip that you broke off? Did you get a new one or did you just not use one?

yellowrocket

hi, know this is an older post. I am replacing my heater core on my '72 with A/C and was interested where you purchased your seal kit thru. I have another question on the defrost door , the screw that goes thru the sheet metal cover plate to the passenger side of the vacuum diaphram on the rear of the box does that act as a stop to keep the door from closing tightly to the top of the box? I removed mine by accident and didn't take notice if the door closed tight or if the screw acts as a stop.

Miles71

Try OPGI.com

https://www.opgi.com/product.asp?item=CH17468

I Replaced my Non-AC core on a 1970 CS. It was quite easy.
Sorry, no info on the Sheet metal screw.

Heat Transfer issues:
The overall design of the Heater box is poor.
The design allows Heat from the Firewall and hot-water core, to easily transfer to the Cool air side, when the box is set for Vent Mode.
Example [Non-AC or AC car, Results are similar].
Assume you are driving on the highway at 65.
Assume the outside air temperature is 80F.
Non-AC car, set the Heat lever set to Cold, measure the temperature from the defroster vent.
The temperate will be about 20 degrees higher than the outside temperate.

AC car, Measure the temperature from the center vent.
The temperate will be about 20 degrees higher than the outside temperate.

Heat from the Engine firewall and from the Heater core, will warm up the cool air in vent mode.
I glued in a few extra ices of foam/foil insulation around the heater core [did not notice any real improvement]







It will allow Heat from the heater core to wa

Roqetman

Hey O’s Car, Great pics! I know this is an old post but I’ve got to replace the heater core in my ‘72 Cutlass Convertible. What, if anything has to be removed from under the hood to get the heat core out, other than the heaters hoses? I read the the AC housing and inner fender have to be removed. Thank you! Roqetman.

Fun71

FYI, that "one time use clip" has been taken off and put back on 6 or 7 times on my car. You just need to be very careful when removing it. If you aren't the patient type, replacement clips called push nuts are available at the local hardware store.

Roquetman,
On the engine side, around the perimeter of the HVAC box, there are four studs with speed nuts holding the heater box to the inside of the firewall (in a square pattern, with a threaded stud on each corner). The top two and lower inside nuts are visible and easily removed, but that outer lower one is hidden behind the fender liner.

The inner fender liner does not necessarily have to be removed to get at that nut. I was able to loosen the bolts that hold the fender liner in, bend the rear of the liner away from the firewall area, reach into the gap with a wrench, and remove the nut. I opted to NOT reinstall that nut upon reassembly, which made subsequent heater core replacements much easier.

Roqetman

Hey Fun71, that’s sounds better than I thought at first but the housing around the AC stuff under the hood has to come off too, right?

Fun71

For a heater core replacement, no. The heater box drops out in the passengers footwell. If you have bucket seats, removing the passengers seat gives you a lot more room to work.

Roqetman

Great, thank you!

Oldssupreme

Excellent Thread! Thanks Rob! Just to be sure, as roquetman asked, to just replace the heater core on my 1972 cutlass supreme with a/c, I take out the entire box with the air ducts and controls that runs from the center to the passenger side under the dash that was shown in the photos from under the dash but I need to remove one hard to access nut from the engine bay side of the firewall? Nothing else needs to come off of the engine bay side of the firewall? I think I left that hard to access nut off when I put the ac box back on the firewall several years ago as per someone’s suggestion on a thread here. Thank you!
chris

Oldssupreme

Hi guys. Can I trouble someone to reiterate the number and location of bolts that I have to remove from the outside air box and the same for the inside heater assembly box in order to access the heater core on my 1972 cutlass with AC? I removed all of the bolts that I can see from the inside and it isn’t budging. There were several bolts that were mentioned in this thread on the outside AC air box as “unnecessary for this job” so I’m a little confused. Thank you!
Chris

Oldssupreme

OK so just to summarize, I got the box out on the outside by removing the four speed nuts that are on the studs poking through the firewall. The four studs poking through the firewall belong to the inside box, but they cannot be removed from the firewall until those five speed nuts are removed from the engine base side, as well as the twoBolts on the inside heater box attached to the firewall. Thanks for your help guys!