Front passenger side floor (under the hood)
If you have a plugged AC condensation drain, clear water will back up and end up on the passenger floor. If the heater core is leaking engine coolant you will have engine coolant end up on the passenger floor.
The heater blower motor is on the interior passenger side. It is kind of a round shaped housing facing the floor.
Blow compressed air into drain tube or use a coat hanger to clear out tube. Usually leaves, debris, and the occasional spider nest will clog the hole and cause the condensation to collect and then drain onto the passenger floor inside the vehicle. After clearing run the vehicle and turn on a/c on high and on recirc. Watch for condensation to now leak out of the drain tube and onto the ground.
Look under the back seat. That's where mine is in my 1999. Pull out the back seat (very easy..two tabs, one on each side...pull them forward and it will release from the clips) it should be right in the center of the floor.
It fastens to a pass through stud at the passenger floor.
For me it's sound like you have problems with the right door. Check the rubber/palstic parts around the door.
with a floor jack.
Move the drivers seat all the way back. Laying down on the drivers side floor mat look up to your left and towards the back of the vehicle you will see two(2) connectors. The connector that is next to the trim panel is the diagnostic connector
Are you running the air conditioner? If the drain line is plugged, it will leak water (condensation) onto the passenger side floor.
Tricked Out - 2004 Mitsubishi Eclipse Diamond Plate Floor-Mats 1-11 was released on: USA: 2005
The Battery is located in the Floor board between the driver and passenger seats, you will have to remove the rubber floor to access it. Special tools you may need are on the passenger side in the floor, where the jack is.