This article is from the Chrysler-Plymouth-Dodge FAQ, by Dr. David Zatz with numerous contributions by others.
Bob Meyer <robert_(e-mail address removed)> writes: If the fluid is
antifreeze (green, sweet smell, hot), you may have a heater core leak (or
loose hose connections). If the fluid is water, most likely the AC
condensation tube is blocked (note: this refers to a
Sundance/Shadow/Duster). When the AC runs on a humid day, a puddle of water
should form underneath this drain if it is working correctly. Look on the
firewall behind and below the power steering pump - you should find a
rubber tube. Make sure that nothing is blocking the tip. If this doesn't
help, you may have a bunch of leaves and junk inside blocking it. Some
times you can back flush it with a garden hose or fish out the leaves with
a wire. If the condensation drain is open and working, and you still have
water on the floor, make sure the cowl drains are clear. The last thing
would be to check the gasket that seals the blower fan (under and behind
the glove box). If this is leaking, loosen the accessable lower screws,
force a bit of strip caulk into the seal gap, and retighten.