I have a Fiat Ducato 2006 Motor Home. The inside/outside Air Vent control lever works perfect up to around 60km/h.
As the speed increases up to 100km/h, the "air control lever" has difficulty staying in the "Inside Air" position.
It appears the outside air pressure is exerting too much pressure on the vent flap.
The local Fiat Service Centre is unable to fix the problem.
Any suggestions?

Is there any way of adjusting the control? or could there be something that's got in there from outside preventing full travel of the flap?
It sounds as though it's not just getting far enough to 'locate'.

There's no way for owners to make adjustments. Initially the agent removed some leaves and said that was the cause, but the problem was still there. He claims he contacted Fiat with no success.
I'm curious to know if other owners have the same problem.