1997 dodge ram B2500 van heating issue

Cold air issue (without seeing your van) is probably the dog house gasket leaking air. As for the valve- again we need more diagnostic help but if you apply vac to the nipple on the valve and it does not move then it’s bad. I just did the one on my 86 van. It leaked vac like mad. The system is very simple. You may have other issues like stated above but you need a service manual for the vac flow chart.
Syleng1