Originally Posted by XR GT
If you slide the leaver from hot to cold it makes no difference.
I think the root of your problem will be the supply of Vacuum to the system. There should be two rubber hoses coming through the firewall - one will go to the removed water valve and the other one should connect to a plastic fitting on the manifold. (That should be your main supply).
I don't know if the system works with the valve removed but when you move the lever from hot to cold, this pushes down on a small plunger / air valve (you'll see it if you remove the glovebox) I know that in my XD when that one failed I had no heat inside the car.
Hope it helps