My vaccum locks have been actin up as long as I had the car, a 1978 300D (123 chasis). I finally broke down and tested the system. The pump put out a nice vaccum. The doors are not leaking. The cruise controll is disconnected and not leaking. The pump shut of actuator is not engaged untill the engine is turned of, so no vaccum leak there.
THE only thing that leaks is the green line, which is the climate controll. With the line plugged into the system I can only build up 5-9 inches of vaccum at idle. With the line disconnected I can build vaccum at a rate of about 1 inch per 10 seconds, at idle.
What is the most likely place to start looking for leaks on the climate controll system? The vaccum switches?