The problem: hvac stuck in defrost and selector had no effect.
Despite strong vacuum in the engine bay, none is getting to the vacuum servo that controls vent selection.
The solution: the servo is up under the dash on the drivers side right of the accelerator and 6 to 8 inches up. There's a red vacuum tube leading into the bottom of it. On top is a lever that you can pull down and direct air to the vents facing you on the dash. Wrap a ziptie around the top of the lever (its horizontal for a couple of inches) and secure it either around the bottom of the servo (can slip off) or through the bracket below.
