The A/C hose can be the cause as it can get kinked and block water from condensation on the evaporator from getting out. So, that is good that has been ruled out.
The other way water can get in on that side is through the fresh air intake under the cowl in front of the windshield.
A few things can cause this;
Improperly replaced windshield that is not sealed.
Wreck damage that loosens up a, "Gutter" that keeps water from flowing into the air passage and allows it to drip in either by dripping past a mounting plug that holds it in place or if it is loose enough, past the gutter guard itself.
The air box has weep holes at either end that drain out near the top rear of each fender well. Sometimes debris can pass through the box cover, the plastic cowl in front of the windshield which sometimes also covers the windshield wipers when they are all the way down, as the box cover can keep larger beris out, it can't keep smaller debris from passing through the grate and that will build up and clog the weep holes.
The cowl is not sealed off in some way. The cowl can be in as many as three pieces that are all held in place with plastic plugs, much like the plug that hold in interior panels. The plugs can get loose or just be defective and allow water to drip from an area where it can get into the passage which is right above the passenger side footwell. If any of the three, the last of which is the aoforementioned gutter guard, are not sealed, water can get into the air passage. Thisis especially true of the top cowl piece as it also has a rubber gasket that runs along the top to keep out water that sheds off the windshield.
The rubber gasket can also come off or fail in some place and allow too much water in for the weep holes to be able to drain out in time before water can overflow the gutter guard into the air passage.
Check the water and make sure it is not anti-freeze. If it is then the heater core is leaking.
That is about all that generally will cause that type of leak and the only way to truly know what is going on is to take off the cowl and the lower A/C evapaorator and heater core cover and inspect everything and put it back together with all new plugs.
Sunday, November 13th, 2011 AT 4:48 PM