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: 87,025 mi (12,500 mi - 126,000 mi)
Visitor, 1999 Dodge Neon, 68,000 mi
water leak on passenger side under dash when A/C on. Eventually blower motor went bad.
Visitor, 2004 Dodge Neon, 109,000 mi
Every time it rains the passenger side fills up with water
Visitor, 2004 Dodge Neon, 85,000 mi
Dodge Neon rain water seems to come from under dash and collects on passenger floor. During hard rains, comes into driver's side floorboard. Last week, water appeared in both doors' speakers. Have been to two windshield places and two dealers and noone can find a problem. Still not fixed.
Visitor, 1999 Dodge Neon, 125,000 mi
inside of dodge neon carpets are flooding water pouring onto floor from under dash. ruined my floors.
same problem, not fixed.... would like to know how to get fixed
Visitor, 2005 Dodge Neon
passenger side front floor board wet don't know where the water was coming from.
Visitor, 2001 Dodge Neon, 12,500 mi
just bought the car and noticed it, the person i got it from took it to her mechanic. he blew the line out with air compressor .... no problems since,,,,so far