It's getting cold out so I hooked the heater core back up just now. I get hot air out of the defrost dash vents, but the gimbel vents and the center console vents blow cold. It looks like the flapper duct valves are actuating but they dont change things much. I did remove an aftermarket AC unit, would that change the hot air flow? Do I need something to take the place of the AC evaporator box?

Sorry, that is just the way that the car works. The dash vents only blow cold air. When you switch from "Vent" to "Heat" the lever actuates a door that redirects the incoming air from the dash vents to the heater core box. From there you can select the hot air to either the defroster or the floor. You cannot direct hot air to the dash vents.

It seems like a strange system to us today, but 40 years ago this was common. I was actually shocked when my 1976 Volvo could direct heated air to the dash vents. I had never seen such a "luxury" before.

Well, I guess thats good and bad, it means one less thing to fix, but cold air blowing on my hands all winter long. (sigh).......................I HATE F#$KING WINTER!

When you set the top lever to "Heat" there shouldn't be ANY air coming out of the dash vents.

I suspect there's some rotted weather stripping stuff on the various air handler doors that would otherwise seal them tight. Mine blows a bit of cool air out the dashboard vents too. Another project, someday!

I suspect Fast woman has hit the nail on the head, a project to address if the dash ever has to come out for more pressing reasons.

I don't think the dash has to come out to access this diverter flap and renew the gasket material. I could be wrong, but you can just unbolt the heater box from the firewall, disconnect the diverter flap actuation cable from the right side of heater box, remove air ducting (don't forget to take out small retainer screws that secure the ducting) and drop the heater box. It's been a while since I have done this so recall might be kind of sketchy, but no need to take out dash I am quite sure.

Dan

My apologies to all. My above post is not accurate. After taking a closer look at my car, the diverter flap that changes from vent to heat is, indeed, behind the center air control panel and incorporated in the heater box. This would most likely require removal of dash for easy access to the heater box. Again, sorry for the mis-information by relying on a fragile memory.

Dan

The temps were in the 20's here this morning, so when I got to the shop (and warmed my hands up) looked into this again. There is no way to get to the flapper that I can see without at least removing the console and loosening the dash. so I stuck foam balls in the vent ducts and backer rods in the center vent defuser. I hope this works.

It is possible to do without taking the dash out. Im restoring my blower and other heating related components. But you need to remove the console, which aint that bad.