Trying to get the heater working

I always have to go through the vacuum and switch stuff "step by step." Best advice I can offer is to read the manual, section on AC. Buried in there, somewhere, is diagrams and descriptions of the switch functions in various switch positions.

You should not need the vacuum can to get it working, but you DO need whatever hose that leads to the interior, hooked to manifold vacuum, or the doors will never position correctly