1997 dodge ram B2500 van heating issue

If it doesn't move with the vacuum disconnected it is no good. If it moves you could have a bad switch or a vacuum hose on wrong. Eliminate it and see if you have heat.

My 03 truck just had a no heat issue. I parked it on a hill face up . Cracked the cap and squeezed the upper hose to get the air out of the heater core. Read it on line and it worked.