If there is a water leak into the passenger side of the interior, under the dash panel, it may be the HVAC housing drain is plugged or restricted.Google+
Car Problem Reports
Dodge Neon Water Leak Due to Plugged AC Drain
Dodge Neon Problem
Average Mileage: 70,500 mi (68,000 mi - 73,000 mi)
Visitor, 1999 Dodge Neon, 68,000 mi
water leak on passenger side under dash when A/C on. Eventually blower motor went bad.