OK, here's your answer. The red/blue line goes to the side nipple on the vacuum element. This is the "small lift" portion of the vacuum element. This line is connected to spot #7 on the vacuum valve. The red/white line goes to the bottom nipple on the vacuum element. This is the "large lift" portion of the vacuum element. It is connected to spot #5 on the vacuum valve.

You'll find the system operates as follows. When the car is first started and the aircon switched on, #5 will have vacuum, #7 will not. This will close the defroster flaps about 85% of the way, leaving just a bit of refrigerated air directed to the windshield. It will remain in that mode for ~30 seconds, then #7 will be activated, completely closing the defroster flaps. Both #5 and #7 must have vacuum to completely shut off flow to the defroster nozzles.

A common failure is for the small lift portion of the vacuum element to fail. When this happens, the defroster flaps don't quite close all the way. Enough cold air is directed to the windshield that condensation forms on the outside of the windshield on warm, humid mornings. I've seen bunches of older MBs driving around like that. Replacement of the vacuum element is the cure.

My $.02 worth of rambling commentary,

- JimY