Strange AC Problem

I was wondering if someone could help me. When my 380sl is cold in the morning and the AC is on, the air stream from the center vents is strong and cold. However, shortly after the thermostat opens, the airstream warms up and slows to a trickle. In addition, the blower only operates at one speed, but I can't tell whether it's high or low, and I don't hear any clicking sound when I switch between High to Low AC.

Anybody have any ideas what the problem is?

Thanks