My wife's 2005 Xterra leaks air through the dash defroster ducts onto the windshield. This happens when the direction for air flow is toward the floor. The dealerships says this is normal and there is no remedy. The leak causes condensation in summer and winter with the accompanying air temperatures from the vehicle.
This is by design. My manual (admittedly for an Altima) clearly states that the floor mode sends a small amount of air to the defrost vents.
The reason for condensation is that you are running the AIR CONDITIONER through the HEAT VENTS. The heat (floor) setting allows a small amount of air to travel to the windshield in order to keep it clear during winter months.
Moving the control to the "vent" setting, where a/c is intended to operate, will eliminate this issue.
Willy
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