I have recently inherited a 99 Passat Wagon. Noticed standing water in passenger side floor boards. Condensation is running onto pavenment, does not appear to be an issue. Pollen filter and seal also seem to fine. Only happens when ac is running. Can't find anything online to help with this. Thanks!
I'm pretty sure you may have the same issue I've had on my Jetta. You're probably going to need to clean the A/C lines or get under the dash and see where your leak is coming from. Mine came from the trays that guide the water from the condenser out of the car. Good luck.
The list in the post above is a fairly complete checkoff.
When I recently had damp floors, to solve the problem I personally checked the sunroof drains (#1), the plenum (#4, twice yearly routine maintenance for me), and the door drain holes (#5).
After preventatively fixing the pollen filter gasket (#3, replaced), and the ECU gasket (#7, replaced), it turned out that redoing the window regulator seals (#2, in all 4 doors) finally solved the problem entirely before the CCM showed any symptoms.