It's very possibly a function of condensation. Check for multiple evaporators. If there is more than one in your Riveria, the second will be somewhere in the area where you are getting the water. If that's the cause, clear the condensate drain and that should clear the problem. This is a very interesting question. I have a 1995 Riviera, in excellent condition, and noticed water beneath the passenger seat and also on the carpet directly behind the seat. After soaking up the water and drying it out thoroughly, I went through a car wash the other day and as the water was spraying underneather the vehicle, immediately I felt the carpet under the passenger seat becoming very wet. I assumed that the water was getting in somewhere under the passenger seat but after the car was put up on a hoist, the meachanic couldn't see where the water was getting into the car under the passenger seat. He has suggested removing the passenger seat and lifting the carpet to see where it might be getting in. He said there are two seals located under the seat with caulking around them and he can only figure that the caulking has let go. However you are relating this problem to the A/C and now have me thinking. Do you think it has to do with the car wash pressures pushing its' way in under the passenger seat or are you thinking that it has to do with the A/C?
Passenger side floorboard, behind the carpet. You can't miss it.
passenger side floorboard, under carpet or behind trim molding on the right side of floorboard
Passenger side floorboard,underneath/behind the glovebox.3 bolts have it mounted.
It is on the passenger side floorboard behind the kick plate( which will be on the right)
passenger side pannel by floorboard / behind side pannel just below heater core.
It is under a plastic cover behind the passenger side headlamp assembly.
Behind the driver's seat under the floor. Pull the carpet back to expose the battery hatch in the upper left corner of the passenger area floorboard.
Behind radio on floorboard.
pull the horn relay -- under black plastic cover (fuse relay unit behind passenger headlight in engine bay).
There is usually a plastic mud guard behind the tire. Keeps some of the road dirt off the belts.
On the right side of the floorboard, front passenger seat there is a triangular shaped piece of plastic. Remove this plastic, there is the reset button behind it, firmly press down the button to reset
There is no 2005 Ford Windstar. In 2004 the name was changed to Freestar. The switch will be in one of these locations. Under dash on passenger side, just past the transmission hump, or console, on the upper part of the floorboard, behind the passenger kick panel, or in the trunk.