Hi all

I have the familiar problem of not having air coming through my center vents. Today I was looking around at the vacuum lines and trying to follow this diagram of the climate vent control vacuum system, but I am confused. If you would be so kind as to take a look at this diagram, maybe you understand it enough to help me get through this.

I want to understand actuator 38, which has two vacuum connectors. What is the side connector (hose labeled "rt/hbl", which I think is German for Red/Light Blue) for? It leads to another device (no. 45a), which connects to the line labeled "rt/sw" (red/black in German), and we cannot find any line with black on it.

There is also a kind of junction block (no. 16/15/13/14 in diagram) which I don't understand. There are two connectors on the top with "-" and two with "+". Does that mean negative and positive pressure? And, there is a common line (rt/gn, or red/green) that leads up to part 35. Is that where the vacuum is generated?

Finally, on my heater box, I noticed that there is an inlet on the front, to which a short red/yellow hose is attached. This hose leads to an actuator (I believe it's the defrost vane actuator) right next to it through a 3-way connector, the third hose being red and white, leading back across the dash to the junction box behind the glove compartment.

I am more or less mechanically inclined, and I'm led to believe there's a leak or a faulty actuator, but to diagnose it properly I would like to understand the workings of the system so I can test out things. For example, we directly connected the red/green hose right onto the red/white one leading to the defrost actuator, and it closed it for us. Then we manually opened up the center vent, and we have air, but of course this is no permanent fix.

Thanks for the help! Look forward to trying to fix this!