If the HVAC (heater) housing is not properly sealed at the bulkhead (firewall), water can leak into the passenger compartment. Foam sealant should be used to seal any gaps and the evaporator drain tube can be modified to prevent further water entry.
Car Problem Reports
Chrysler Pacifica Water Leak Due to HVAC Case Not Sealed at Bulkhead
Chrysler Pacifica Problem
Visitor, 2004 Chrysler Pacifica
passenger side floor is always wet, have taken it to 2 different mechanics to be "fixed" and still, it's always wet. Now I can tell the Dealership exactly what the problem is, word for word... hopefully this time it will be fixed correctly!