Help with wierd AC problem request on 1983 300D
 

Friends:

My AC has been fine, until a couple of weeks ago. Now, it seems when I slow down, hot air comes out of the driver's vent and the left most center vent, and cold air comes out of the passenger side vent and the right most center vent. This car (1983 300D) doesn't have, as far as I can tell, a left/right setting (as did my earlier 1979 240D). This also seems to happen once I reduce speed. What gives? What could this be due to?
Any help and advice is greatly appreciated, thanks so much in advance!:confused:

bump

Only three Choices
 

1.Mono-Valve (I'm gonna pick this one)Reduced Electrical power @ lower RPMs.
2.Vacuum Pods
3.CCU unit

Vacuum
 

My theory is a vacuum leak that is letting one or more pods go back to the resting position when the engine is turning slowly and making less vacuum. Very possibly a leaky diaphragm in one of the pods.