How do you fix a leaky windshield under the dash on the passenger side?

Answer 1

It's probably not the windshield. Either one of your door wells are filled up with leaves, or you have a bad heater core.

I have a 92 grand am which leaked on the passenger side i took off the cowl and noticed an air exchanger that controls the air coming from the outside of the car for fresh air. i took out that assemby and notice water had been getting in from under the exchanger, a foam gasket on bottom failed so i used silicon caulk and lined the foam gasket and replaced it . i have not had water in the cars since. :) Also check just ubnder the blower motor for the fan there is a rubber door like thing there. sometimes leaves block that hole you can fish out the leaves with your fingers .