Interior condensation after heavy rains, floorboards in front would be soaked. mechanic removed cowling, cleared internal gutter system and resealed everything. today windows covered inside with condensation and with low temps, made it almost impossible to drive.

If the car has a rear heater, maybe the matrix is leaking... If the car has a sliding sunroof it might be a displaced drain causing the problem. Such sunroofs can store a significant amount of rainwater in the gutters unless the car is perfectly level.

One side only or both? Do you have a sunroof? Clogged drain vent for sunroof, cowl, A/C, bad weatherstrip?

1: heater core leaks. (green water)
2: A/C condensate tray drain plugged.
3: or its rain water, if rain water, the windshield cracked?
3a: the cowl is full of leaves and now the cowl vents are packed and the drains are plugged up there, (look in cowl vents) see flood?

if not using A/C at all its the heater.

After a heavy rain, I noticed about 2 inches of water on the rear passenger floorboards of my '02 Signature TC. The front was also soaked.

Try this link at Edmunds' forum - http://townhall-talk.edmunds.com/direct/view/.f147dda/0 - it discusses various leaks the town car has. A little way into the thread, it specifically discusses the leak on the passenger side. My leak was coming in through the foam gasket under the HVAC (air vent assembly). After reading the entire thread, I concluded my problem could be fixed by following Ralka's instructions on page three, reply #25. The whole repair took just over an hour - I'm not a mechanic, so if you're mechanically inclined, it would probably take less time. It fixed the problem.

PS - I also had to replace two plastic, rectangular cowl retainer clips (with plastic screws), they're made by Dorman (the 41099 cowl retainer fit perfectly, in spite of a link they have that says it's not made for the TC). If you also need to replace the clips, you can get them here - http://www.autopartswarehouse.com/search/?searchType=global&Ntt=cowel+retainer&N=0&submit=Submit+Query.

Good luck.

a couple things to look at if it has a sunroof the sun roof would have drain hoses that run down in each corner next you need to look at the cowl this is the section in front of the windshield that has a drain on it as well if you find nothing there the next step would be to remove the seats and carpet and sit in the car while running water over it either way you should remove the carpet and make sure it is dry all the way threw or mold will start to grow and you will never get ride of it not good for your heath other key spots to look at is if the windshield was ever replaced it could be a poor seal

If you remove the door rails at the bottom of the doors you'll be able to lift the carpet and visually look for some small drain plug devices. It sounds like one or more of them is missing or that you have lost a seal in the door or window.

try having an assistant 'water'' your car with a garden hose while you're in it.especially check seals at windshield & doors.it could take a few minutes of ''watering'' before a leak shows up.

The tubing under the dash that comes from the air condition may be stopped up...there may be leafs or trash stopping up hole along the wind shield (Miada convertable problem) if this is the problem flush out the tubes...or your wind shield may be leaking ('87 chevy problem) if it is the windshield try cleaning around and resealing...Mine stopped when I had to have new windshields put in...

check the seal on the cabin air filter.there is a gasket that sits infront the will leak if its not in place

sounds like you have a window seal leak.  The only other way water will leak into the car is a leaky heater core or a clogged A/C drain.  Do you have a sun roof that could be leaking?  As they have drains too.