My son's air conditioning is leaking inside of his car on the passenger side. The floor is soaked. Any suggestions on what to do to stop this or what is causing it? When he uses the heater, he has no problems.

Evaporator drain is plugged. Take a wire or very long pipe cleaner and insert it into the drain (3/8" black tube) under the car. Reach under car from passenger side. Be prepared for a lot of water to gush out.

It's more than likely the a/c overflow tube stopped-up. Clean it with a small wire. Good luck

Yeah what he said, lol.