What is this for?

[BeeKool]

I think I've asked this before, but what's the purpose of this hole in the firewall?

(Rectangular one between the heater core nipples and the ac evaporator nipples)

Is the thin thermocouple from the interior on the heater/a.c. box suppose to protrude through the firewall?
Do most of you simply fabricate a nice looking piece of sheetmetal and cover it?

 

[PP1RT]

Mixer valve

 

[Mark B]

The temp control/heater valve with the capilary tube mounts there.

 

[Sixpactogo]

If you have no plans to use the heater or the AC I guess you could remove the heater box and plug all 4 holes

 

[Demonic]

You'll meed some heater hoses first, lol. The seal in the heater valve gets old and leaks, silently, soaking the firewall insulation and your carpet as it runs down the inside of the firewall. The seal is available from NAPA. Replacing it is not for the faint of heart. You have to bend 4 tabs to separate the valve from the B body plate, and hope they don't snap when you bend them back. Care, caution, and patience, a bit of finesse is needed.

https://www.napaonline.com/en/p/BK_6601000?searchCategory=5.6&searchIndex=App

The valve body, the Ranco H-10, was used by other car manufacturers with wound up HVAC engineers like Chrysler had. LOL! Late 50's Chevy and Studebaker, among others. I've found NOS ones for other makes at Hershey Fall meet. E-bay might be your best bet if you're doing a restoration.

 

[BeeKool]

I rebuilt the heater/ac box last winter.
I plan on converting the ac to a modern classic/vintage air system.
So if that's a necessary part, where do I find one and how does it plumb?

 

[BeeKool]

Also I couldn't help but notice the ballast resistor in the picture Dale posted.
Does an MSD Ready to Run ignition do away with the resistor?

 

[Sixpactogo]

Vintage air has a complete setup with Heater box, controller and compressor that eliminates your whole factory system.If you use their complete AC you would remove your heater box and install theirs. If you want to use your heater box with a aftermarket compressor you will still need the Ranco valve assembly that regulates the water to your factory heater core. That thermocouple that you mentioned hooks up to that valve as well as the temp control from you heater control. I'm not sure what year car you are working on but the 70 Ranco valve is different from 68 - 69 cars.

 

[Tim Chavez]

Also I couldn't help but notice the ballast resistor in the picture Dale posted.
Does an MSD Ready to Run ignition do away with the resistor?

my Msd r2r still runs through the resistor.

 

[BeeKool]

Vintage air has a complete setup with Heater box, controller and compressor that eliminates your whole factory system.If you use their complete AC you would remove your heater box and install theirs. If you want to use your heater box with a aftermarket compressor you will still need the Ranco valve assembly that regulates the water to your factory heater core. That thermocouple that you mentioned hooks up to that valve as well as the temp control from you heater control. I'm not sure what year car you are working on but the 70 Ranco valve is different from 68 - 69 cars.

70 Coronet.
I would like to reuse my original heater box beings I spent several hours and a few hundred dollars rebuilding it. I was able to reuse the original core and evaporator.
It must be Classic Air tha I was looking into in a CI magazine.
Has everything from the firewall forward.

 

[JimKueneman]

You will need that to connect the temperature cable to so you can shut off the coolant flow to the heater.

 

[Sixpactogo]

70 Coronet.
I would like to reuse my original heater box beings I spent several hours and a few hundred dollars rebuilding it. I was able to reuse the original core and evaporator.
It must be Classic Air tha I was looking into in a CI magazine.
Has everything from the firewall forward.

In 1970 they changed the valve by adding a vacuum pod to it. I just looked on Ebay and there are a couple of NOS units on there. One is pretty reasonable at $265.00 Type in Mopar PN 3441414 and it should show up. Otherwise, you could call Jim Tucker in Calif. He rebuilds them and may have one for you. His number is 760 749 3488. He rebuilt one for me for about half of what that new one is. Either way you will need one with the plan you have.