Tankertoad1

I have a '76 that has pretty good insulation under the carpet and dash/firewall. I put exhaust wrap from the rams head manifolds to the mufflers (may do ceramic headers later on, $$$). I installed a hot water shutoff valve to the heater core, and I wrapped the entire AC box in Reflectix. All is working pretty well, and I am getting good cold air from the AC.....the Texas heat is just around the corner.
Next I need to work on the fresh air door in the passenger kick panel. I haven't opened it up yet, but with a flashlight I can tell the foam is missing and there is a significant gap around the door to let in hot air. I read on here about the "craft foam" and pop rivet fix for that.....but here is my question.
With the car off, the vent door is closed. With the car running and the air selector in the OFF or MAX AC positions, the door opens up. If I select Normal AC, Vent, or Bi-Level, the door drives closed. Is this working correctly?
Last week on a cool evening, I had the wife drive home from dinner (scarry I know). I sat in the passenger seat with all the air off, and I could not believe how much hot air comes out of that vent. It felt like a hair dryer blowing on my legs, and you can feel it on your shoulder from the drivers seat, even with the T-tops off.
I guess the solution (after replacing the foam seal) is to always select vent or normal AC to avoid the hot blast.
Any other solutions/ work arounds out there? I thought about sealing the door off, but decided against it. My guess is that it keeps exhaust from entering and making you sleepy.

dry

I too will be following this post for sure.......

BHRIG

You can also get a foam heat collar from most vendors which fits behind engine at firewall on top of transmission.......it greatly reduces unwanted heat in cabin.

Good Luck

Tankertoad1

I forgot to mention that. The transmission tunnel foam is going to be in my next parts order.

speedreed8

that fresh air door picks up air from the cowling area. make sure your seal is in place and in good shape on the rear of the hood. the trans. foam collar helps alot also.

Aflac

lots of interest on this by me as well...

speedreed8

.....but here is my question.
With the car off, the vent door is closed. With the car running and the air selector in the OFF or MAX AC positions, the door opens up. If I select Normal AC, Vent, or Bi-Level, the door drives closed. Is this working correctly?

i believe its working correctly, the door in the passenger side opens in max AC, it becomes the return air drawing cool air from inside, in normal AC it closes and the other door in the fender well opens to allow fresh air from the cowling area to enter.

i had to replace the foam seal on my door (79).

dgood

to replace the foam in the door, once you pull it from your car, drill out the rivets that hold the sides together. separate them and replace them with foam from Michaels and rivet the pieces back together. it is 99 cents for a full sheet (12X18). it is called fun foam (creatology). Just did the door in my 79 last week and you would not believe how much air it stops. If you buy the foam from a vendor, it is 9.99 plus shipping.

7T1vette

The foam seal material is identical to the "craft foam" [black] sheets found at Michael's Crafts Store. You only need one sheet for that job.

The outside air inlet door (under cowl area in right fender) and the kickpanel door both operate via the same vacuum signal. When control head is in "OFF" or "MAX" position, the cowl door should be 'open' and the kickpanel door 'closed'. In all other control head positions, the position of those doors is reversed. So, if the kickpanel door is 'open' when in "OFF" or "MAX" position, there is no vacuum getting to that servo...or the servo is damaged or stuck...or the control head vacuum distribution manifold is not working as intended. The best reference document for working on your A/C system is the Chevrolet Chassis Service Manual (which I am referencing as I type). If you have one, refer to Sect. 15, page 65 (Figure 50).

Tankertoad1

7T1vette ,
That was my guess, but I think you confirmed it. The actuator in the kick panel is working, since I can see the door open and close as I roll the selector through various settings. It must be vacuum or signal related.
I don't have the book you are referencing, but it might be worth getting to figure this out once and for all.
I found some posts on this subject going back to 2002 and there seems to be some conflicting info on how it's all supposed to work.
I just can't believe I would ever want that door open. There is that much hot air coming from it. Another old post suggests using windshield adhesive to caulk around the plenum (behind the lower flapper door). That might be the key to keeping the heat out of that area.

hammadown

My car is a 72
I always thought that if you select MAX/RECIRCULATE that the cowl flapper shuts to stop outside/engine/heat air from getting in and OPENS the interior kick panel flap so that the cooled cabin air gets recirculated back to the plenum/blower housing? thats how it works on modern systems.when in anything but max/recirculation the right kick panel flap should be closed and the cowl feeds the plenum/blower housing.

this is how mine works but...........I have a lazy kick panel sevo because the servo for the cowl has the DREADED restricted vacuum source. in max/recirculate the vacuum isn't strong enough to open the kick panel flap after supplying the cowl servo with vacuum to shut its flapper and hold it shut...... but if I reach down and push the kick flap open, it opens with out effort. there is just not enough vacuuum for the servo to open it with the cowl servo using the same vacume source closing the cowl flapper at the same time. if I take the vacuum hose off the kick servo or take it out of MAX/REC the kick flapper shuts instantly. theres enough vacuum to hold it open ...but not enough to open it.
this seems to be a common problem with our systems and the vacuum line to the cowl flapper is the reason. another member ran a dedicated vacuum line to the cowl flapper and the flapper worked as designed with enough vacuum to open the kick flap. but the stock vacuum line was the problem and I have it too. so when I run my A/C I ALWAYS put in on MAX and I just reach over and push open the kick flapper. oh well........

Hammadown

jb78L-82

Just a further suggestion to maximize the A/C effectiveness where you are: Install a manual shutoff valve under the hood in place of the vacuum operating one that controls the coolant going to the heater core in these cars and many GM cars of the era. That way you can completely shutoff the flow of hot water flowing through the heater core during the hot weather. The OEM ones never completely close and the engines heat is constantly diluting the A/C. I did this 30 years ago on my mom's 72 Caprice and later on my 78 in 1986. Between the added interior insulation, the shutoff valve, the Dewitts radiator and Stewart stage 2 water pump, on a 90 degree day with the A/C off, I feel no engine heat coming into the cabin from the outside-the shutoff valve is one of the keys to stop the hot air intrusion into the cabin.

20mercury

On my 76, basis research on this forum, I did:

*foam trans collar
*Insulation in the trans tunnel (you can buy these preformed from Corvette vendors)
*hot water valve (one hose only) from Lowes
*Reflextix from Lowes (under carpet everywhere)
*disconnected or fixed the outside air door in front of the drivers side so that it is closed all of the time.
*new rubber seals on clutch linkage and tried to make sure all firewall holes were sealed.

This seemed to improve things a lot after wilting my sister in law for a test ride. My a/c is not working yet and I live in South Louisiana so I can relate to Denton.

Good luck and hope this helps. Also welcome other suggestions too!
Sorta now, or at least much improved!

Tankertoad1

The debate continues.........
And of all the old posts I have read the consensus is about 50/50 for each side of the argument.
Can anybody with a detailed enough book or diagram set me strait once and for all. (And maybe it is different for different years?)
On a '76, with the air setting in OFF or MAX AC, should the passenger side kick panel door be open or shut? And in the rest of the positions down the control wheel...should be the opposite?

hammadown

In MAX/RECIRCULATE the COWL door in the fenderwell should be CLOSED to keep outside/fresh/engine heated air from making its way into the plenum/evaporater/fan box and the inside kick panel flap should be OPEN to RECIRCULATE the cabin air back into the plenum/evaperator /fan box

Hammadown

MotorHead

I just stuffed some of the pipe insulating stuff behind the engine in the tunnel ,5 bucks. I also halve the tunnel insulated under the car with something silver can't remember the name but it was fairly thick with the thickness due to the adhesive ( which has its own characteristics ).

My heater is shut off or should I say the heater and all the hoses won't be doing anything from up in the attic, still numbers matching car if you have all the parts and a coupe of years to restore it ( just a joke I could care less if it was NM ) .

Mine stays pretty cool, matter of fact I don't even think about it. Now if I lived in south where the lows for the day are in the 100's then things might be different

Tankertoad1

I just replaced the foam seal on the kickplate flapper door and I sealed the plenum seam between the body and the flapper door. There was a 1/4 to 1/2 inch gap between the body fiberglass (behind the passenger side "Stingray" emblem down towards the frame)and the fiberglass off the firewall/dash. That is where the blow dryer like air was coming from when the kick panel door is open and I am cruising down the road. Air off the engine and exhaust, mixed with ram air, was blowing through that seam and coming in the kick panel vent. I used a roll of windshield caulk that another forum member suggested in a previous post. It's a sticky black putty that you press in the gap.
I'll take her for a spin next week and see if it all worked, then report back.

Tankertoad1

Success....I took her out last night and the hot air from the kick panel was greatly reduced when the lower kick panel door is open (air system off). Looks like sealing the plenum seam was the trick there. When the air is selected to Normal AC or Vent, the new foam seal around that door works like a champ. No air gets in when that door is closed.
The only heat I could feel was radiating from the center console. I have a transmission tunnel foam collar ordered. I'll put it in next week and see if that works. At least the AC or vent air right now is enough to overcome the leaking and radiating hot air that I had before. It should be a much more pleasant car this summer than it was last year.
Many thanks to all the fine forum folks that steered me in the right direction to get this done!