I have a new Phaeton that my wife and I are really enjoying this year. It is built on a Freightliner chassis. One issue however is that while traveling on the road using the chassis powered air conditioner, we experience very heavy condensation on the duct work under the dash - so much so that we have to put towels down on the floor to catch all the "rain". The a/c checks out fine relative to presure differentials and air flow and thermostatic control of the evaporator to prevent it from freezing up.
My only remaining possibility is an air leak from somewhere at the front of the coach that is coming in under the dash which is being blown across the ducts and as this is warm humid air, it condenses on the ducts.
The fresh air duct is kept closed during ac operation.
So.....where is the air getting through? Can't find anything obvious so any suggestions on a "hidden air passage?