Passenger side firewall down low should see a small water tube drain that can get clogged. I have use a small bit of wire, like coat hanger, to reach in and move around easily to allow flow. Watch out though, water can come rushing out of the hole. When people park after using the a/c there will be a puddle of water that drains on to the ground when it is not clogged. It is the evaporator sweating.