ventilation system problems

I have a problem that I can't eaaly trace. When the ventilation is on two problems arise. One is vaccum system, after beeing on for a while it sends the air to the windshield regards less of the setting on the lever. It goes back to normal after a while but then goes to the windshield again. It has something to do with the vaccum system I think but not sure.

Problem number two involves the a/c. when engaged for a while it throws the tranmission to hell. The symptom is that there is a great loss of power and the engine runs at very high rpms. The gears change very late and the car feels like it has no power at all. If I turn the a/c off, even to ventilation all symptoms clear after about 30-60 seconds and the cars runs normal again.

any ideas??? :confused:

Check the small vacuum tube where it comes out of the intake manifold valve. there is a small plastic tube between two rubber fittings on the right side of engine on top nect to carburator.