ALL OF THE DIAGRAMS IN THIS FIRST POST ARE NOT THE CORRECT WAY TO HOOK IT UP. THEY REPRESENT THE BENTLEY AND KAMMY "METHODS." See this post (within this thread) for the final proper hookup!
So... there seems to be much confusion and many people saying that Bentley is wrong in their diagram.
I'm going to prove, here and now, that they are not incorrect (I'm not saying they're correct either!) in their diagram, and hypothesize how this thing is really supposed to have you operate it.
I took apart my vacuum distributor to find out how it worked. It's rather simple really but requires a little bit of analysis to determine what it routes where and when.
Instead of taking pictures, in order to line things up I actually scanned the surfaces involved.
The bottom black part that the hoses connect to, without the white part on top:
Notice the little bity holes in the surface there. Those go to their closest hose connectors.
The top part, inside, rotated to represent the third (center-most) "Blue Spot" on the lever (remember you're looking at it from underneath here!)
Now the analysis. I mirrored the top part verticaly, aligned it to be on the same axis as the bottom, and rotated it to represent each of the positions on the lever. To see where the vacuum is going, I made little dots representative of where the holes on the bottom part are.
Yellow - Air recirculation; with vacuum, air is recirculated, no vacuum, no recirculation
Red - Center defrost/vent flap, with vacuum, air comes out center vents, without vacuum, air comes out defrost vents
Green - Bentley "vacuum boost" (I'll explain this later), Kammy hose from tank
Blue - Bentley hose from tank, Kammy footwell vent
Cyan - Bentley footwell vent, Kammy vacuum boost
I will reference some things here:
Bentley diagram -- diagram found on page 12-13 of the Bentley manual.
Kammy diagram -- http://dana.ucc.nau.edu/~kaw5/...m.jpg
The Manual -- the manual that comes with cabriolets from the dealer, essentially the "how it all should work"
In these images the arrows are reversed, since vacuum is the reverse of pressure, but I find it easier to think of in terms of the arrows pointing away from the source of vacuum.
Here we go.
Position 1, farthest left blue spot:
In this position it appears that it's set to do ... hmm... nothing. At all. vacuum is routed back through the center, meaning the vacuum escapes. If we were using Kammy's diagram instead, the vacuum would be closing the air recirculation flap to recirculate air, and opening the center vents. This actually fits the description of this position in the VW manual (the little silver one that comes with the car).
Position 2, middle blue spot:
In this position, again, we're doing nothing if we use Bentley's diagram. Air routed to center escapes.
In Kammy's diagram, the air is routed to a channel that escapes through the outside of the circle, which is confusing to me; I'm wondering if that outside area is meant to be vacuum tight, because most certainly it is not and would be very hard to make so. If it was vacuum tight, it would open the footwell vents.
Neither of these match the functions described in the manual -- since it says "air outlets" are the same as the first position which would have center vents open. This doesn't do that.
Position 3, last blue spot:
Using the bentley diagram this would have the center and air recirculation flaps operating. But that doesn't match the functions described in the manual either. To do that it would need to route it to the cyan outlet. Kammy's diagram would have it escaping once again going to the outer rim, and if vacuum tight, opening the footwell vents, which is half correct. If the vacuum booster works the way I think it does, it might then come back in through the port that the bentley connects the tank to and then also open the center vents. I still have to do some testing on the whole "vacuum booster" thing...
Position 4, first black spot:
According to bentley this would have air going to the outer rim and going to *both* of the ports of the footwell servo, one of which is supposed to be the vacuum booster return! Kammy's would have it doing the same thing just using different ports.
Kammy's would have it doing the same thing.
Position 5, middle black spot:
This is where bentley starts making a little sense. It routes the vacuum to the footwell vent servo and the air recirculation servo. The manual says fresh air is circulated, however. So this works only half way. If we use Kammy's diagram, we have escaping air (center vents opening if the outside rim holds vacuum)
Position 6, last black spot, defrost:
Another dead spot in the Bentley manual but this actually is how it's supposed to work. Kammy's is also dead (again, unless the outer rim is supposed to hold vacuum, in which case it would open the center vents and footwell vents, both wrong!)
Conclusion from this analysis? They're both totally wrong, according to The Manual. Bentley is just "Less wrong"
One thing that needs to be addressed is the green spot on this. According to bentley that's the "vacuum boost", where I assume vacuum from the footwell servo is fed back through to operate other things. The only problem is that if we use Bentley's diagram, that will escape right away unless the outer rim is vacuum tight which it is not.
I'm working on other arrangements that tries to make use of that vacuum boost, so stay tuned. We might be able to figure out the right arrangement knowing how the distributor distributes things.
Modified by Legoguy at 7:03 PM 10-18-2006
Updated with new images and corrections because apparently vaccum *is* supposed to be held throughout the outer rim (don't ask me how!)
Modified by Legoguy at 6:50 PM 10-20-2006