What does this vent control do?

[geoff]

I took my '08 Cayenne S in for the 12K mile service this week, and asked the service advisor about something I haven't been able to figure out. He looked in the owners manual (which I had read), and couldn't figure it out either. I've had the car since May, and still can't tell what the thing does. I circled it in picture with yellow and red:

The 2 dash vents controls labeled A control air flow out the center. What does the other A dial control? It does not appear to do anything for the windshield air flow!

[mudman2]

windscreen air

I took my '08 Cayenne S in for the 12K mile service this week, and asked the service advisor about something I haven't been able to figure out. He looked in the owners manual (which I had read), and couldn't figure it out either. I've had the car since May, and still can't tell what the thing does. I circled it in picture with yellow and red:

The 2 dash vents controls labeled A control air flow out the center. What does the other A dial control? It does not appear to do anything for the windshield air flow!

[dfkeller]

windscreen air

I took my '08 Cayenne S in for the 12K mile service this week, and asked the service advisor about something I haven't been able to figure out. He looked in the owners manual (which I had read), and couldn't figure it out either. I've had the car since May, and still can't tell what the thing does. I circled it in picture with yellow and red:

The 2 dash vents controls labeled A control air flow out the center. What does the other A dial control? It does not appear to do anything for the windshield air flow!

The 'a' dial controls the air flowing from the grill where it is to the windshield. as well as i can figure, it is used to keep the dash area cool and to counter the heat from constant sunshine. you can check by placing tissue paper over the vent grill and see if rotating the 'a' control makes a difference in air moving out of the grill there.