Changing the heater control valve, or even having the wrong one, won't affect the switching of airflow in the dash. Sounds like either the vacuum switch at the heater controls isn't working or has one or more broken off nipples, or there's a vacuum hose popped off one or more of the actuators on the heater box. Those are a PITA to try and check with the dash/heater box in the car. Hopefully, the photos I posted of my extra heater box will show you which hose goes to which valve.