Water is draining on the floor from my car ac, what is causing this?

check the drain hose and internal drain for the ac as if the gunk builds up inside the ac box the condensation will over flow into the cabin

Usually if the drain tube for the AC is plugged the front passenger floor gets wet, not the rear.

You probably have two different issues here.
The water on the floor is usually caused by a drain tube being stopped up. The tube is supposed to let the water drain out of the car and onto the ground. It should be on the bottom of the firewall or below the floor.
You would need to have the computer scanned for trouble codes to find out why the check engine light is coming on.

The ac drain hose is either clogged up or missing, causing the flow of water on the passenger's side floor. Have the drain hose checked.

HEATER CORE AND AC EVAPORATOR DRAIN TUBE STOPPED UP ALLOWING AC CONDENSATING WATER OR SWEAT TO RUN IN FLOOR BOARD.OR LEAKING HEATER CORE WILL CAUSE WATER OR ANTIFREEZE IN FLOOR BOARD.

have the AC evaporator (found under the dash) inspected. It may need cleaning or the drains may have fallen out of place.

You will have to blow out the drain ,there is a drain ,that is stopped up,look under the hood,below where the ac lines go in the firewall into the car,it will be there,use compressed air,like a air tank.

Clogged or disconnected drain hose from the heater core box. Or bad/leaking heater core. Does the liquid smell like coolant. If so bad heater core. If not and the water only when you use the AC then it is a drain hose issue. If neither of those pan out you could have a leaky windshield. However 99% of the time a wet passenger floor is caused by a bad heater core or drain hose.

Most likely the windshield is starting to leak -
Second choice is - there is a drain hose - it may be clocked up - please pull up the floor man - and look for a rubber hose that goes down through the floor board.
If that hose is clogged it will only be wet when you run the AC and you will notice not much water coming from under the car from the drain hose which exits under where the passengers feet are.

Best of it - hope this helps

have you looked at the weld between the inner wing and the bulkhead under the hood? We had the same problem and that's where the problem was