Help with A/C and heater hose footwell routing

[Jameel]

I'm trying to figure out how to route my HVAC hoses in my footwells. Its an '83 SC with factory A/C.

I took the carpet pocket out and the large plastic wye fittings on both sides are just plain cooked at this point. They are cracked and new ones are like $500. No thanks. I'm looking to simplify this setup.

First off, this is how I'm thinking the system is working. The heat from the back of the car (red lines) comes up through those plastic wye's #35 and #36 and then through the small wyes #40 and out the corner dash vents. This is for defrost for the doors. The A/C gets fed through the small hoses to the small wye #40 and out the same vents. Is this correct?



Here's a pic of my setup right now. (The small wye #40 and hoses to the steel body ducts are not in this picture.) and colored lines to illustrate how I think it works.



Here's the passenger side. This time the small #40 wye and hoses are there, but I've removed the big plastic wye. You can see the open end of the large hose coming down from the dash and the steel pipe poking up from the longitudinal.



So there's an integral steel duct coming down from the underside of the dash that's not hooked to anything. Green arrow. I don't know what this is for, and I don't know that it's ever been hooked up to anything. What is this for?





If I'm correct about how this all routes, I'm thinking that I can simply run a hose from the longitudinal heat duct straight up to the dash, and then run only the A/C lines to the corner vents. This would eliminate all of the wyes entirely, but also NOT feed heat to the corner vents. I don't really care about the latter. I park the car in the winter and I think I've actually needed defrosting maybe twice in 35,000 miles. This would be same setup (I think?) as what my brother has on his '79 SC. The '79 had factory A/C, but no wye's going to the corner vents. It looks like the corner vents in cars with A/C got assigned A/C duties only, while cars without A/C got assigned fresh/heat to the corner vents. Makes sense from the diagrams in this post.



So, goal is to do the setup that's in my bro's '79 SC. Thoughts?

[Jameel]

Anyone out there with some thoughts on this? Be great to hear from you.

[frankc]

If you want to retrofit an earlier HVAC system, the info I posted when documenting the A/C delete retrofit from my '77 may be of benefit to you:

Retrofitting non-A/C ventilation ducts