I have a 1998 motorhome built on an E350 chassis, with the V10 engine.
After driving for any amount of time, the carpets get very wet. I'm suspecting A/C, as it's definitely water (not coolant, washer fluid or anything else). It happens if it's dry, so it's not rainwater leaking or splashing.
The carpet on the passenger side gets very slightly damp. The driver's side gets SOAKING wet, all the way from the very top (underneath the pedals) down to the front of the seat mounts. Under the seat, the carpet remains dry.
I figured that it was going to be A/C evaporator drain water, but I checked, and the drain on the blower housing (on the passenger side) is clear, and it drips water copiously directly onto the ground (like it should) when the A/C is running. And that is on the passenger side, so I have no idea how water could be getting over to the driver's side. I have the service manual for this truck, and according to it, all the evaporator and drain is on the passenger side.
I do not see evidence of water coming from any vent or anywhere above the carpet.
So...any guesses as where this is coming from, and how I get it to stop?

 

Sometimes we use a little talcum powder sprayed across the area where we suspect a possible entrance of water. That most times tells us where to get to work.