April 22, 2011I`m getting some water hitting the passengerside floor mat coming from underneath the dash. It isn`t the heater core because it only happens during a rain or wash. I raised the wiper on the passengerside and held the water hose at the bottom of the windshield going back and forth from the middle of the windshield to the passengerside fender. I did this for about 2 or 3 minutes, opened the door, and I saw the water dripping. I don`t see any water on the firewall afterwards from underneath the hood, so I don`t think the water is going through a hole. I haven`t had time to check it, but someone told me today that it could be coming through the return air vent located underneath the wipers. Any thoughts?
I forgot to mention that the truck is a 1998 GMC Sierra if that helps any.