When my ac is on why does water come up through the carpet on the passenger side

Hello, when the air conditioner operates, the function of the evaporator core acts as a heat exchanger -- it removes hot moist air from the vehicle interior and gets rid of it -- creating condensation, which means there is water that must evacuate from the heater plenum behind the dash. This is typically done via a drain tube that exits through the floor of the vehicle. For your concern, either the drain tube is restricted, causing the water to overflow, or the drain tube is dislodged, allowing the water to hit the floor. Check the drain tube to make sure it's free of restrictions and routed properly. www.repairpal.com/repair-shops See a local shop near you if needed for assistance.