The condensate from your AC evaporator drains thru a tube which sticks straight thru the firewall. It's on the passenger side about 2/3 down the firewall. Water ususally dribbles out and drops, but it will often creep back along the underside of the tube. The gasket at the firewall is made of the same space age Martian grade A bull5hit as the dashboards were, i.e. it isn't very good. Water gets wicked back thru the gasket and runs under the carpet.
If you can find the right size, stick a 90 degree elbow on the end of the tube to prevent water from creeping back. A short piece of flexible tubing may work as well. If you can't find the right elbow, silicon the snot outta the penetration from inside the cab. If memory serves, you have to pull the blower motor off from below the dash to see the penetration from the inside. Pop up the corner of the carpet and padding from under the trim. Use a shop vac or towels to mop up the puddle you're gonna find. Leave it popped for a few days and it should dry out. Hit it with Ozium if it still stinks. I had to do this on my 01 Ram. Also happened to my brother's Durango.
