Jetta air diffuser - how it works

[Von Richthofen]

As indicated by Buckets the diffuser is the path of least resistance & so most of the air flow that normally goes through the two centre face vents will go through the diffuser when the diffuser is open.

The comment you made: "If I use footwell + front, it will go to footwell + diffuser unless I manually shut off the rollers on the diffuser." is correct. Except that I would add that it also goes to the two outer face vents as well.

I'm sure the face vent button is only there to use in combination with other buttons, that the default air flow, when no buttons are pushed, is via the face vents & that the two centre face vents & the diffuser are connected and the combined air flow between them is controlled soley by the roller.

[Buckets]

Don't you love having the ability to embed video!
Anyway, back to the issue at hand. I've had the dash apart a couple of times and seen how it all works....the face level vents and the diffuser run off the same duct, therefore they will always share the airflow. The roller switch will determine where the lion's share of air will go.

Spiff, what happens when you press, say the footwell button? Does the air to the diffuser/face vents stop and go to where you've selected?

[spiff]

Don't you love having the ability to embed video!
Spiff, what happens when you press, say the footwell button? Does the air to the diffuser/face vents stop and go to where you've selected?

Yes! i'm loving this video embedding. Lots of time saved.

When I press footwell, it goes to the footwell and the diffuser stops.
When I press footwell + front, it goes to the footwell and diffuser.

Can anyone tell I'm trying hard to find out how I managed to get what I (twice) experienced before?
I might have to take it apart, even though I don't know what I'm looking for.