PA 28 Warrior floor heat duct question

It seems as though the shut-off valve for the heater system is only
controlling the passenger-side heat duct on the floor of my '74 Warrior.

The pilot's side is hot to the touch, whereas the passenger side is
relatively cool to the touch. I can shut the small pilot-side floor vent so
the hot air doesn't come in the cabin, but the hot air inside the duct heats
it to a point where it makes my feet warm.

It seems as though this floor has some sort of divider running through it.

The main control valve (that apparently controls the overall flow of hot air
to the cabin through this duct) is in the engine compartment. I have taken
off the main hose that comes from the heat exchanger and felt inside this
control box. It feels as though there is a large flap-type valve, and it
appears to be fully closed (at least that is what it feels like.) I am not
sure if this valve is also split? I cannot feel far enough inside the unit
to be sure.

Does any of this make sense? Ideas for how to correct it?

Thanks.