03 Windstar A/C air moves from dash to floor

[TimStout]

Hi,
Just found the forum and have read a bunch of A/C issues (with great help) but have not found anything about the problem I'm seeing. Hope someone can help!
Just the other day the wife was driving down the road and the A/C stopped blowing cold air and the vehicle smelled funny. I checked things out right away as the temps here were above 95 degrees. I found a few problems:
1. Oil fill cap was not screwed on right...no oil leak but I suspect the engine was seeing a lean or rich situation and was running hot. The smell was anti-freeze. Wife thinks the temp gauge was normal but doesn't knowfor sure.
2. The A/C was a little low on R-134 so I added a little.
3. The A/C starts out running cool but while driving down the road the cool air switches from the dash vents to the floor vents and gets warm to hot and then switches back again.

I wondering if the vacuum supply line from the engine to the A/C controls could have melted?
Can anyone tell me where the line starts from and goes through the fire wall at?
Thanks much for the help!