How to control rear/roof heater?

[drk]

My kombi is factory fitted with a rear heater and 2 way ducting (roof and rear). The controls only allow me to set the temp and fan speed.

I can see the servo in the heater but how do I get it to switch between the rear and roof vents? Its currently fixed/set to rear.

 

[roadtripper]

I have the Caravelle with the rear heater but it's also 3 zone Aircon and that has additional controls.

I suspect for a single control you'll find the hot air comes from the floor duct by the bottom of the C pillar and the cold air comes from the roof vents, depending on where you set it.

That's the arrangement that mine seems to have in the back, I've never noticed hot air from above or cold air from below.