I tried bench testing both valves. When applying 12V there is no current draw, no sounds and no change in the routing of the vaccum (still goes from U to F ports). So maybe they are both broken?
The male and female connectors do not have a tab or notch to ensure polarity. I didn't notice any markings but I didn't check that well. A quick Google search seems to indicate that polarity is not important for solenoid valves. Not sure if that is really true or not.Do you have service manual article 83-020? It shows how they are wired and it looks like the pins on those switchover valves are polarity dependent.
Thanks!! I have bought it. AndyAndy,
This item from eBay is cheap, from a reputable vendor. The picture has the yellow and green items I think you found and 2 types of Pierburg switchover valves that our cars use. The one with the white cap I believe could be used on the left side (closest to the heater vacuum element). Maybe that white cap is just a filter for ambient air venting.
79 Mercedes R107 450SL Climate Control Valve Assembly